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/rateLimit.test.ts

@@ -1,6 +1,10 @@
 import { beforeEach, describe, expect, it } from 'bun:test';
 import { config } from '../src/env';
-import { checkRateLimit, cleanupRateLimitCache, clearRateLimitCache } from '../src/utils/rateLimit';
+import {
+  checkRateLimit,
+  cleanupRateLimitCache,
+  clearRateLimitCache,
+} from '../src/interfaces/http/middleware/rate-limit';
 
 describe('Rate Limiter', () => {
   beforeEach(() => {