log(app): add warnings to silent except Exception blocks

- Internal tool auth header failure now logs a warning instead of
  silently passing, making auth bypass easier to spot in logs.
- Token last_used_at update failure now logs at DEBUG (fire-and-forget,
  non-critical, but useful when debugging token tracking issues).
- Image ownership verification failure now logs a warning so unexpected
  access-check errors surface instead of silently allowing the request.

app.py

@@ -331,8 +331,8 @@ if AUTH_ENABLED:
                         request.state.current_user = "internal-tool"
                     request.state.api_token = False
                     return await call_next(request)
-            except Exception:
-                pass
+            except Exception as _e:
+                logger.warning("Internal tool auth header check failed: %s", _e)
             # Allow DIRECT localhost requests (internal service calls from
             # heartbeats etc.). Tunnel/proxy-forwarded requests are excluded by
             # _is_trusted_loopback so LOCALHOST_BYPASS can't be abused over a
@@ -385,11 +385,10 @@ if AUTH_ENABLED:
                                     _db.close()
                             try:
                                 await _asyncio.to_thread(_do)
-                            except Exception:
-                                pass
+                            except Exception as _e:
+                                logger.debug("Failed to update token last_used_at: %s", _e)
                         _asyncio.create_task(_touch_last_used(matched_id))
                         # Keep bearer-token callers out of normal cookie/user
-                        # routes. API-aware routes can read api_token_owner.
                         request.state.current_user = "api"
                         request.state.api_token = True
                         request.state.api_token_id = matched_id
@@ -464,8 +463,8 @@ async def serve_generated_image(filename: str, request: Request):
                 _db.close()
     except HTTPException:
         raise
-    except Exception:
-        pass
+    except Exception as _e:
+        logger.warning("Image ownership verification failed for %r: %s", filename, _e)
     ext = filename.rsplit('.', 1)[-1].lower()
     mime = {
         "png": "image/png", "jpg": "image/jpeg", "jpeg": "image/jpeg",