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/db.test.ts

@@ -1,6 +1,6 @@
 import { describe, expect, it } from 'bun:test';
-import { db, files } from '../src/db/index';
-import { files as schemaFiles } from '../src/db/schema';
+import { db, files } from '../src/infrastructure/persistence/drizzle/index';
+import { files as schemaFiles } from '../src/infrastructure/persistence/drizzle/schema';
 
 describe('Database Layer', () => {
   it('should export db instance', () => {