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/schemas/test.py

@@ -266,7 +266,7 @@ class TestOut(BaseModel):
             if hasattr(obj, "technique") and obj.technique is not None:
                 obj.__dict__["technique_mitre_id"] = obj.technique.mitre_id
                 obj.__dict__["technique_name"] = obj.technique.name
-        except Exception:
+        except Exception:  # nosec B110
             pass  # DetachedInstanceError or similar — leave technique fields None
 
         # Only split evidences when they are already in memory (loaded via joinedload)