補強 cache best-effort 診斷

services/cache_manager.py

@@ -8,10 +8,14 @@ module-level cache 收斂到這裡，避免各 route 各自持有一份 dict。
 """
 
 import os
+import logging
 import time
 from pathlib import Path
 
 
+logger = logging.getLogger(__name__)
+
+
 class FingerprintCache:
     """TTL + fingerprint 的小型 in-memory cache。"""
 
@@ -30,13 +34,14 @@ class FingerprintCache:
             if self._fp_fn() != entry['fp']:
                 return None
         except Exception:
-            pass
+            logger.debug("cache fingerprint check failed for %s", self.name, exc_info=True)
         return entry['data']
 
     def set(self, key, data):
         try:
             fp = self._fp_fn()
         except Exception:
+            logger.debug("cache fingerprint write failed for %s", self.name, exc_info=True)
             fp = None
         self._store[key] = {'data': data, 'ts': time.time(), 'fp': fp}
 
@@ -137,4 +142,4 @@ def clear_dashboard_cache():
     except FileNotFoundError:
         pass
     except OSError:
-        pass
+        logger.debug("dashboard shared cache cleanup failed", exc_info=True)