feat: add detailed request logging to /api/score and global 422 handler

- Log incoming request (client, content-type, metrics, has_gt) on each /api/score call
- Log scoring result (latency, skipped metrics, scores) on success
- Register global RequestValidationError handler: logs url/content-type/errors
  so 422 causes are visible in server log without checking HTTP response body
- Fix jsonable_encoder for exc.errors() to handle non-serializable ctx objects

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

webapp/api/score.py

@@ -2,10 +2,13 @@
 
 from __future__ import annotations
 
+import logging
 import time
 from typing import Annotated
 
-from fastapi import APIRouter, Header, HTTPException
+from fastapi import APIRouter, Header, HTTPException, Request
+from fastapi.exceptions import RequestValidationError
+from fastapi.responses import JSONResponse
 
 from rag_eval.metrics.weights import compute_weighted_score
 from rag_eval.settings import EvaluationSettings
@@ -13,6 +16,7 @@ from webapp.models import ScoreRequest, ScoreResponse
 from webapp.services.inline_scorer import inline_scorer
 
 router = APIRouter(prefix="/api/score", tags=["score"])
+logger = logging.getLogger("webapp.api.score")
 
 
 def _get_settings() -> EvaluationSettings:
@@ -58,6 +62,7 @@ def _check_auth(authorization: str | None, token: str) -> None:
     },
 )
 def score_sample(
+    raw_request: Request,
     request: ScoreRequest,
     authorization: Annotated[str | None, Header()] = None,
 ) -> ScoreResponse:
@@ -88,6 +93,15 @@ def score_sample(
     **鉴权**：若 `.env` 中配置了 `SCORE_API_TOKEN`，需在请求头携带
     `Authorization: Bearer <token>`；留空则无需鉴权（适合内网部署）。
     """
+    client = f"{raw_request.client.host}:{raw_request.client.port}" if raw_request.client else "unknown"
+    logger.info(
+        "[score] incoming  client=%s  method=%s  content_type=%s  metrics=%s  has_gt=%s",
+        client,
+        raw_request.method,
+        raw_request.headers.get("content-type", ""),
+        request.metrics,
+        request.ground_truth is not None,
+    )
     settings = _get_settings()
 
     # Require Bearer auth only when the deployment configured a shared token.
@@ -141,6 +155,12 @@ def score_sample(
         {},
     )
 
+    logger.info(
+        "[score] done  latency=%dms  skipped=%s  scores=%s",
+        latency_ms,
+        skipped,
+        {k: (round(v, 4) if v is not None else None) for k, v in all_scores.items()},
+    )
     return ScoreResponse(
         scores=all_scores,
         weighted_score=round(weighted, 4) if weighted is not None else None,