Implements HTTP Basic Authentication for Cloudflare Pages Functions. Provides `authenticated(request, env)` that checks `Authorization` header against environment variables (`BASIC_USER`/`BASIC_PASS` or `UPLOAD_BASIC_USER`/`UPLOAD_BASIC_PASS`). Returns `true/false` and a standard 401 response helper. This is a self-contained, reusable auth module that can be dropped into any Pages Functions project requiring simple credential checks, without pulling in external auth libraries.

Acts as a storage provider registry. Exports a function `getProvider(env)` that reads the `STORAGE_PROVIDER` env var and returns the appropriate module (telegram or r2). Each provider must implement `key`, `validateConfig`, `upload`, and `fetchFile`. This clean provider pattern allows adding new storage backends (e.g., S3, local filesystem) by simply dropping in a new file with the same interface and registering it. The abstraction decouples upload/serving logic from storage details, making the system extensible and testable.

Provides `createMockKV()` which returns an in-memory implementation of a KV namespace with `get`, `put`, `delete`, `list` methods and operation tracking (tracking count per method). Also includes `createMockCtx()` and `createMockEnv()` helpers. This utility is used across all unit tests to simulate Cloudflare KV bindings without network calls. It is a self-contained, reusable test helper that can be extracted for any Cloudflare Workers or Pages project needing a lightweight KV mock.