refactor(pipeline): migrate ws egress to Redis Pub/Sub and optimize A…

[aniebietafia]

…I translation pipeline

• Replace per-user AIOKafkaConsumer in WebSocket routers with Redis Pub/Sub subscriptions for room-specific audio egress (pipeline:audio:{room_code}) and captions (pipeline:captions:{room_code}).
• Refactor TranslationWorker to perform translations concurrently with asyncio.gather, and add per-language error resilience.
• Add client-side buffering to STTWorker with a periodic stale buffer sweeping/cleanup mechanism.
• Implement persistent HTTP connections (connection pooling) across DeepL, OpenAI TTS, and Voice.ai clients via a singleton client pattern.
• Scale pipeline Kafka topics to 3 partitions for horizontal worker scaling.
• Mock Redis client and Connection Manager in unit tests, fix STT buffering assertions, and resolve all 205 test failures.
• Add comprehensive docs/frontend-angular-integration.md guide.
• Format all files and resolve Ruff lints.

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Configuration used: defaults

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📥 Commits

Reviewing files that changed from the base of the PR and between aeb3a7d and 3d968ca.

📒 Files selected for processing (23)

• app/core/config.py
• app/db/session.py
• app/external_services/deepgram/service.py
• app/external_services/deepl/service.py
• app/external_services/openai_tts/service.py
• app/external_services/voiceai/service.py
• app/kafka/consumer.py
• app/kafka/manager.py
• app/modules/auth/constants.py
• app/modules/meeting/constants.py
• app/modules/meeting/schemas.py
• app/modules/meeting/state.py
• app/modules/meeting/ws_dependencies.py
• app/modules/meeting/ws_router.py
• app/schemas/pipeline.py
• app/services/audio_bridge.py
• app/services/stt_worker.py
• app/services/translation_worker.py
• app/services/tts_worker.py
• tests/meeting/test_ws_router.py
• tests/test_core/__init__.py
• tests/test_kafka/__init__.py
• tests/test_kafka/test_pipeline.py

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/audio_transcribe_pipeline

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