➕(summmary) add Langfuse to summary service dependencies

Install Langfuse observability client in summary service
to enable LLM tracing, monitoring, and debugging capabilities
for AI-powered summarization workflows,
improving visibility into model performance and behavior.

src/summary/pyproject.toml

@@ -15,6 +15,7 @@ dependencies = [
     "posthog==6.9.1",
     "requests==2.32.5",
     "sentry-sdk[fastapi, celery]==2.43.0",
+    "langfuse==3.10.6"
 ]
 
 [project.optional-dependencies]

src/summary/summary/core/config.py

@@ -4,6 +4,7 @@ from functools import lru_cache
 from typing import Annotated, List, Optional
 
 from fastapi import Depends
+from pydantic import SecretStr
 from pydantic_settings import BaseSettings, SettingsConfigDict
 
 
@@ -77,6 +78,12 @@ class Settings(BaseSettings):
     posthog_event_failure: str = "transcript-failure"
     posthog_event_success: str = "transcript-success"
 
+    # Langfuse (LLM Observability)
+    langfuse_enabled: bool = False
+    langfuse_host: Optional[str] = None
+    langfuse_public_key: Optional[str] = None
+    langfuse_secret_key: Optional[SecretStr] = None
+
     # TaskTracker
     task_tracker_redis_url: str = "redis://redis/0"
     task_tracker_prefix: str = "task_metadata:"