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/infrastructure/router/cascade.py

@@ -304,7 +304,8 @@ class CascadeRouter:
                 url = provider.url or "http://localhost:11434"
                 response = requests.get(f"{url}/api/tags", timeout=5)
                 return response.status_code == 200
-            except Exception:
+            except Exception as exc:
+                logger.debug("Ollama provider check error: %s", exc)
                 return False
 
         elif provider.type == "airllm":