feat(observability): structured logs, W3C trace IDs, Sentry hooks (#18)

- TS: pino + pino-http; every HTTP request log includes traceId from
  W3C traceparent header (generated if absent); forwarded to ml/serving
  on all /score, /generate, /reward, and /api/ml proxy calls
- Python: structlog JSON; FastAPI middleware binds trace_id via
  contextvars so every log line within a request carries it
- Sentry: optional SENTRY_DSN init in both runtimes (no-op if unset)
- Replace all console.* calls across services/api with pino logger
- Update tests to spy on logger instead of console

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ml/serving/main.py

@@ -34,12 +34,25 @@ from typing import Optional, Deque
 
 import httpx
 import numpy as np
-from fastapi import FastAPI, HTTPException
+import sentry_sdk
+import structlog
+import structlog.contextvars
+from fastapi import FastAPI, HTTPException, Request
 from pydantic import BaseModel
+from starlette.middleware.base import BaseHTTPMiddleware
 
+import logging_config
 import nats_consumer
 from prompts import get_prompt
 
+logging_config.configure()
+
+_SENTRY_DSN = os.getenv("SENTRY_DSN")
+if _SENTRY_DSN:
+    sentry_sdk.init(dsn=_SENTRY_DSN, environment=os.getenv("ENV", "development"))
+
+log = structlog.get_logger()
+
 
 @asynccontextmanager
 async def lifespan(app: FastAPI):
@@ -50,6 +63,21 @@ async def lifespan(app: FastAPI):
 
 app = FastAPI(title="oO ML Serving", version="1.0.0", lifespan=lifespan)
 
+
+class _TracingMiddleware(BaseHTTPMiddleware):
+    async def dispatch(self, request: Request, call_next):
+        structlog.contextvars.clear_contextvars()
+        traceparent = request.headers.get("traceparent", "")
+        if traceparent:
+            parts = traceparent.split("-")
+            trace_id = parts[1] if len(parts) == 4 and len(parts[1]) == 32 else None
+            if trace_id:
+                structlog.contextvars.bind_contextvars(trace_id=trace_id)
+        return await call_next(request)
+
+
+app.add_middleware(_TracingMiddleware)
+
 LITELLM_URL = os.getenv("LITELLM_URL", "http://localhost:4000")
 LITELLM_MASTER_KEY = os.getenv("LITELLM_MASTER_KEY", "sk-oo-dev")