fix: remove UploadBatcher crash window, make bot concurrency configurable, fix all test import paths

- Removed UploadBatcher (src/infrastructure/telegram/upload-batcher.ts + DI):
  pending uploads no longer lost on crash, files sent directly to Telegram
- Changed upload-controller to use Bun.file().stream() instead of createReadStream
- Made PER_BOT_CONCURRENCY configurable via TELEGRAM_BOT_CONCURRENCY env
- Fixed 18 test files with updated import paths and mock shapes
- Updated package.json test script: telegramQueue.test.ts → bot-pool.test.ts
- Build, lint, and test suite all pass

test/file.test.ts

@@ -5,7 +5,7 @@ import {
   extractFileName,
   extractMimeType,
   getFileType,
-} from '../src/utils/file';
+} from '../src/shared/utils/file';
 
 describe('File Utilities', () => {
   describe('getFileType', () => {