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/routers/tests.py

@@ -281,7 +281,7 @@ def create_test(
         from app.services.jira_service import auto_create_test_issue
         auto_create_test_issue(db, test, current_user)
         db.commit()
-    except Exception:
+    except Exception:  # nosec B110
         pass  # jira_service already logs warnings internally
 
     return test
@@ -374,8 +374,8 @@ def create_test_from_template(
         from app.services.jira_service import auto_create_test_issue
         auto_create_test_issue(db, test, current_user)
         db.commit()
-    except Exception:
-        pass
+    except Exception:  # nosec B110
+        pass  # jira_service already logs warnings internally
 
     return test
 
@@ -1485,7 +1485,7 @@ def import_rt(
                     continue
                 try:
                     img_bytes = base64.b64decode(ev.data)
-                except Exception:
+                except Exception:  # nosec B112
                     continue  # malformed base64 — skip
                 if len(img_bytes) > _MAX_EVIDENCE_BYTES:
                     continue  # over size limit — skip
@@ -1493,7 +1493,7 @@ def import_rt(
                 key = f"{test.id}/{uuid.uuid4()}_{safe_name}"
                 try:
                     upload_file(img_bytes, key)
-                except Exception:
+                except Exception:  # nosec B112
                     continue  # storage error — skip but don't abort
                 evidence_obj = Evidence(
                     test_id=test.id,