fix: replace 59 bare except clauses with proper logging (#25)

All `except Exception:` now catch as `except Exception as exc:` with
appropriate logging (warning for critical paths, debug for graceful degradation).

Added logger setup to 4 files that lacked it:
- src/timmy/memory/vector_store.py
- src/dashboard/middleware/csrf.py
- src/dashboard/middleware/security_headers.py
- src/spark/memory.py

31 files changed across timmy core, dashboard, infrastructure, integrations.
Zero bare excepts remain. 1340 tests passing.

src/dashboard/middleware/security_headers.py

@@ -4,10 +4,14 @@ Adds common security headers to all HTTP responses to improve
 application security posture against various attacks.
 """
 
+import logging
+
 from starlette.middleware.base import BaseHTTPMiddleware
 from starlette.requests import Request
 from starlette.responses import Response
 
+logger = logging.getLogger(__name__)
+
 
 class SecurityHeadersMiddleware(BaseHTTPMiddleware):
     """Middleware to add security headers to all responses.
@@ -130,12 +134,8 @@ class SecurityHeadersMiddleware(BaseHTTPMiddleware):
         """
         try:
             response = await call_next(request)
-        except Exception:
-            import logging
-
-            logging.getLogger(__name__).debug(
-                "Upstream error in security headers middleware", exc_info=True
-            )
+        except Exception as exc:
+            logger.debug("Upstream error in security headers middleware: %s", exc)
             from starlette.responses import PlainTextResponse
 
             response = PlainTextResponse("Internal Server Error", status_code=500)