fix(security): resolve Snyk/bandit code analysis findings

- config.py: move REPORT_OUTPUT_DIR from /tmp (world-writable) to /app/reports
  to prevent CWE-377 symlink attack vector (B108, only real security issue)
- main.py: log startup seed failures instead of silently swallowing them (B110)
- Add # nosec annotations to intentional try/except patterns that are by design:
  Jira integration errors, email failures, DetachedInstanceError, storage errors,
  and Jira session timeout (all B110/B112 false positives)
- Add # nosec B105 to false positives where bandit misidentifies config key
  names and masking strings as hardcoded passwords
- Add .bandit config to skip B311 in seed_demo.py (random used for fake
  demo data generation, not cryptographic purposes)

backend/app/services/tempo_service.py

@@ -78,7 +78,7 @@ def _get_tempo_base_url(db=None) -> str:
             ).first()
             if row and row.value:
                 return row.value.rstrip("/")
-        except Exception:
+        except Exception:  # nosec B110
             pass  # DB unavailable — fall through to defaults
 
     env_url = getattr(settings, "TEMPO_BASE_URL", None)