chore: initialize backend structure with TypeScript, configuration files, and sample worker

backend/.editorconfig

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+# http://editorconfig.org
+root = true
+
+[*]
+indent_style = tab
+end_of_line = lf
+charset = utf-8
+trim_trailing_whitespace = true
+insert_final_newline = true
+
+[*.yml]
+indent_style = space

backend/.gitignore

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+# Logs
+
+logs
+_.log
+npm-debug.log_
+yarn-debug.log*
+yarn-error.log*
+lerna-debug.log*
+.pnpm-debug.log*
+
+# Diagnostic reports (https://nodejs.org/api/report.html)
+
+report.[0-9]_.[0-9]_.[0-9]_.[0-9]_.json
+
+# Runtime data
+
+pids
+_.pid
+_.seed
+\*.pid.lock
+
+# Directory for instrumented libs generated by jscoverage/JSCover
+
+lib-cov
+
+# Coverage directory used by tools like istanbul
+
+coverage
+\*.lcov
+
+# nyc test coverage
+
+.nyc_output
+
+# Grunt intermediate storage (https://gruntjs.com/creating-plugins#storing-task-files)
+
+.grunt
+
+# Bower dependency directory (https://bower.io/)
+
+bower_components
+
+# node-waf configuration
+
+.lock-wscript
+
+# Compiled binary addons (https://nodejs.org/api/addons.html)
+
+build/Release
+
+# Dependency directories
+
+node_modules/
+jspm_packages/
+
+# Snowpack dependency directory (https://snowpack.dev/)
+
+web_modules/
+
+# TypeScript cache
+
+\*.tsbuildinfo
+
+# Optional npm cache directory
+
+.npm
+
+# Optional eslint cache
+
+.eslintcache
+
+# Optional stylelint cache
+
+.stylelintcache
+
+# Microbundle cache
+
+.rpt2_cache/
+.rts2_cache_cjs/
+.rts2_cache_es/
+.rts2_cache_umd/
+
+# Optional REPL history
+
+.node_repl_history
+
+# Output of 'npm pack'
+
+\*.tgz
+
+# Yarn Integrity file
+
+.yarn-integrity
+
+# dotenv environment variable files
+
+.env
+.env.development.local
+.env.test.local
+.env.production.local
+.env.local
+
+# parcel-bundler cache (https://parceljs.org/)
+
+.cache
+.parcel-cache
+
+# Next.js build output
+
+.next
+out
+
+# Nuxt.js build / generate output
+
+.nuxt
+dist
+
+# Gatsby files
+
+.cache/
+
+# Comment in the public line in if your project uses Gatsby and not Next.js
+
+# https://nextjs.org/blog/next-9-1#public-directory-support
+
+# public
+
+# vuepress build output
+
+.vuepress/dist
+
+# vuepress v2.x temp and cache directory
+
+.temp
+.cache
+
+# Docusaurus cache and generated files
+
+.docusaurus
+
+# Serverless directories
+
+.serverless/
+
+# FuseBox cache
+
+.fusebox/
+
+# DynamoDB Local files
+
+.dynamodb/
+
+# TernJS port file
+
+.tern-port
+
+# Stores VSCode versions used for testing VSCode extensions
+
+.vscode-test
+
+# yarn v2
+
+.yarn/cache
+.yarn/unplugged
+.yarn/build-state.yml
+.yarn/install-state.gz
+.pnp.\*
+
+# wrangler project
+
+.dev.vars
+.wrangler/

backend/.prettierrc

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+{
+	"printWidth": 140,
+	"singleQuote": true,
+	"semi": true,
+	"useTabs": true
+}

backend/package.json

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+{
+  "name": "invoice-issuer",
+  "version": "0.0.0",
+  "private": true,
+  "scripts": {
+    "deploy": "wrangler deploy",
+    "dev": "wrangler dev",
+    "start": "wrangler dev",
+    "test": "vitest",
+    "cf-typegen": "wrangler types"
+  },
+  "devDependencies": {
+    "@cloudflare/vitest-pool-workers": "^0.5.2",
+    "@cloudflare/workers-types": "^4.20250109.0",
+    "typescript": "^5.5.2",
+    "vitest": "2.1.8",
+    "wrangler": "^3.60.3"
+  }
+}

backend/src/index.ts

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+/**
+ * Welcome to Cloudflare Workers! This is your first worker.
+ *
+ * - Run `npm run dev` in your terminal to start a development server
+ * - Open a browser tab at http://localhost:8787/ to see your worker in action
+ * - Run `npm run deploy` to publish your worker
+ *
+ * Bind resources to your worker in `wrangler.toml`. After adding bindings, a type definition for the
+ * `Env` object can be regenerated with `npm run cf-typegen`.
+ *
+ * Learn more at https://developers.cloudflare.com/workers/
+ */
+
+export default {
+	async fetch(request, env, ctx): Promise<Response> {
+		return new Response('Hello World!');
+	},
+} satisfies ExportedHandler<Env>;

backend/test/index.spec.ts

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+// test/index.spec.ts
+import { env, createExecutionContext, waitOnExecutionContext, SELF } from 'cloudflare:test';
+import { describe, it, expect } from 'vitest';
+import worker from '../src/index';
+
+// For now, you'll need to do something like this to get a correctly-typed
+// `Request` to pass to `worker.fetch()`.
+const IncomingRequest = Request<unknown, IncomingRequestCfProperties>;
+
+describe('Hello World worker', () => {
+	it('responds with Hello World! (unit style)', async () => {
+		const request = new IncomingRequest('http://example.com');
+		// Create an empty context to pass to `worker.fetch()`.
+		const ctx = createExecutionContext();
+		const response = await worker.fetch(request, env, ctx);
+		// Wait for all `Promise`s passed to `ctx.waitUntil()` to settle before running test assertions
+		await waitOnExecutionContext(ctx);
+		expect(await response.text()).toMatchInlineSnapshot(`"Hello World!"`);
+	});
+
+	it('responds with Hello World! (integration style)', async () => {
+		const response = await SELF.fetch('https://example.com');
+		expect(await response.text()).toMatchInlineSnapshot(`"Hello World!"`);
+	});
+});

backend/test/tsconfig.json

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+{
+	"extends": "../tsconfig.json",
+	"compilerOptions": {
+		"types": ["@cloudflare/workers-types/experimental", "@cloudflare/vitest-pool-workers"]
+	},
+	"include": ["./**/*.ts", "../worker-configuration.d.ts"],
+	"exclude": []
+}

backend/tsconfig.json

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+{
+	"compilerOptions": {
+		/* Visit https://aka.ms/tsconfig.json to read more about this file */
+
+		/* Set the JavaScript language version for emitted JavaScript and include compatible library declarations. */
+		"target": "es2021",
+		/* Specify a set of bundled library declaration files that describe the target runtime environment. */
+		"lib": ["es2021"],
+		/* Specify what JSX code is generated. */
+		"jsx": "react-jsx",
+
+		/* Specify what module code is generated. */
+		"module": "es2022",
+		/* Specify how TypeScript looks up a file from a given module specifier. */
+		"moduleResolution": "Bundler",
+		/* Specify type package names to be included without being referenced in a source file. */
+		"types": [
+			"@cloudflare/workers-types/2023-07-01"
+		],
+		/* Enable importing .json files */
+		"resolveJsonModule": true,
+
+		/* Allow JavaScript files to be a part of your program. Use the `checkJS` option to get errors from these files. */
+		"allowJs": true,
+		/* Enable error reporting in type-checked JavaScript files. */
+		"checkJs": false,
+
+		/* Disable emitting files from a compilation. */
+		"noEmit": true,
+
+		/* Ensure that each file can be safely transpiled without relying on other imports. */
+		"isolatedModules": true,
+		/* Allow 'import x from y' when a module doesn't have a default export. */
+		"allowSyntheticDefaultImports": true,
+		/* Ensure that casing is correct in imports. */
+		"forceConsistentCasingInFileNames": true,
+
+		/* Enable all strict type-checking options. */
+		"strict": true,
+
+		/* Skip type checking all .d.ts files. */
+		"skipLibCheck": true
+	},
+	"exclude": ["test"],
+	"include": ["worker-configuration.d.ts", "src/**/*.ts"]
+}

backend/vitest.config.mts

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+import { defineWorkersConfig } from '@cloudflare/vitest-pool-workers/config';
+
+export default defineWorkersConfig({
+	test: {
+		poolOptions: {
+			workers: {
+				wrangler: { configPath: './wrangler.toml' },
+			},
+		},
+	},
+});

backend/worker-configuration.d.ts

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+// Generated by Wrangler
+// After adding bindings to `wrangler.toml`, regenerate this interface via `npm run cf-typegen`
+interface Env {
+}

backend/wrangler.toml

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+#:schema node_modules/wrangler/config-schema.json
+name = "invoice-issuer"
+main = "src/index.ts"
+compatibility_date = "2025-01-09"
+
+# Workers Logs
+# Docs: https://developers.cloudflare.com/workers/observability/logs/workers-logs/
+# Configuration: https://developers.cloudflare.com/workers/observability/logs/workers-logs/#enable-workers-logs
+[observability]
+enabled = true
+
+# Automatically place your workloads in an optimal location to minimize latency.
+# If you are running back-end logic in a Worker, running it closer to your back-end infrastructure
+# rather than the end user may result in better performance.
+# Docs: https://developers.cloudflare.com/workers/configuration/smart-placement/#smart-placement
+# [placement]
+# mode = "smart"
+
+# Variable bindings. These are arbitrary, plaintext strings (similar to environment variables)
+# Docs:
+# - https://developers.cloudflare.com/workers/wrangler/configuration/#environment-variables
+# Note: Use secrets to store sensitive data.
+# - https://developers.cloudflare.com/workers/configuration/secrets/
+# [vars]
+# MY_VARIABLE = "production_value"
+
+# Bind the Workers AI model catalog. Run machine learning models, powered by serverless GPUs, on Cloudflare’s global network
+# Docs: https://developers.cloudflare.com/workers/wrangler/configuration/#workers-ai
+# [ai]
+# binding = "AI"
+
+# Bind an Analytics Engine dataset. Use Analytics Engine to write analytics within your Pages Function.
+# Docs: https://developers.cloudflare.com/workers/wrangler/configuration/#analytics-engine-datasets
+# [[analytics_engine_datasets]]
+# binding = "MY_DATASET"
+
+# Bind a headless browser instance running on Cloudflare's global network.
+# Docs: https://developers.cloudflare.com/workers/wrangler/configuration/#browser-rendering
+# [browser]
+# binding = "MY_BROWSER"
+
+# Bind a D1 database. D1 is Cloudflare’s native serverless SQL database.
+# Docs: https://developers.cloudflare.com/workers/wrangler/configuration/#d1-databases
+# [[d1_databases]]
+# binding = "MY_DB"
+# database_name = "my-database"
+# database_id = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+
+# Bind a dispatch namespace. Use Workers for Platforms to deploy serverless functions programmatically on behalf of your customers.
+# Docs: https://developers.cloudflare.com/workers/wrangler/configuration/#dispatch-namespace-bindings-workers-for-platforms
+# [[dispatch_namespaces]]
+# binding = "MY_DISPATCHER"
+# namespace = "my-namespace"
+
+# Bind a Durable Object. Durable objects are a scale-to-zero compute primitive based on the actor model.
+# Durable Objects can live for as long as needed. Use these when you need a long-running "server", such as in realtime apps.
+# Docs: https://developers.cloudflare.com/workers/wrangler/configuration/#durable-objects
+# [[durable_objects.bindings]]
+# name = "MY_DURABLE_OBJECT"
+# class_name = "MyDurableObject"
+
+# Durable Object migrations.
+# Docs: https://developers.cloudflare.com/workers/wrangler/configuration/#migrations
+# [[migrations]]
+# tag = "v1"
+# new_classes = ["MyDurableObject"]
+
+# Bind a Hyperdrive configuration. Use to accelerate access to your existing databases from Cloudflare Workers.
+# Docs: https://developers.cloudflare.com/workers/wrangler/configuration/#hyperdrive
+# [[hyperdrive]]
+# binding = "MY_HYPERDRIVE"
+# id = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
+
+# Bind a KV Namespace. Use KV as persistent storage for small key-value pairs.
+# Docs: https://developers.cloudflare.com/workers/wrangler/configuration/#kv-namespaces
+# [[kv_namespaces]]
+# binding = "MY_KV_NAMESPACE"
+# id = "xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
+
+# Bind an mTLS certificate. Use to present a client certificate when communicating with another service.
+# Docs: https://developers.cloudflare.com/workers/wrangler/configuration/#mtls-certificates
+# [[mtls_certificates]]
+# binding = "MY_CERTIFICATE"
+# certificate_id = "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
+
+# Bind a Queue producer. Use this binding to schedule an arbitrary task that may be processed later by a Queue consumer.
+# Docs: https://developers.cloudflare.com/workers/wrangler/configuration/#queues
+# [[queues.producers]]
+# binding = "MY_QUEUE"
+# queue = "my-queue"
+
+# Bind a Queue consumer. Queue Consumers can retrieve tasks scheduled by Producers to act on them.
+# Docs: https://developers.cloudflare.com/workers/wrangler/configuration/#queues
+# [[queues.consumers]]
+# queue = "my-queue"
+
+# Bind an R2 Bucket. Use R2 to store arbitrarily large blobs of data, such as files.
+# Docs: https://developers.cloudflare.com/workers/wrangler/configuration/#r2-buckets
+# [[r2_buckets]]
+# binding = "MY_BUCKET"
+# bucket_name = "my-bucket"
+
+# Bind another Worker service. Use this binding to call another Worker without network overhead.
+# Docs: https://developers.cloudflare.com/workers/wrangler/configuration/#service-bindings
+# [[services]]
+# binding = "MY_SERVICE"
+# service = "my-service"
+
+# Bind a Vectorize index. Use to store and query vector embeddings for semantic search, classification and other vector search use-cases.
+# Docs: https://developers.cloudflare.com/workers/wrangler/configuration/#vectorize-indexes
+# [[vectorize]]
+# binding = "MY_INDEX"
+# index_name = "my-index"