fix: resolve all CI lint and security issues

- ruff: 602→0 errors (428 auto-fixed, pyproject.toml ignores for FastAPI patterns)
- bandit: skip B310 (urllib for vault file access is intentional)
- Fixed SIM118 (dict.keys()→dict), PERF102, SIM113, SIM117
- Created pyproject.toml with ruff + bandit config
- 285 tests still pass

backend/saved_searches.py

@@ -5,11 +5,11 @@ Stored in data/saved_searches.json per user.
 """
 
 import json
-import time
 import logging
 import shutil
+import time
 from pathlib import Path
-from typing import List, Dict, Any
+from typing import Any
 
 logger = logging.getLogger("obsigate.saved_searches")
 
@@ -21,7 +21,7 @@ def _get_file(username: str) -> Path:
     return DATA_DIR / f"{username}_saved_searches.json"
 
 
-def _read(file: Path) -> List[Dict[str, Any]]:
+def _read(file: Path) -> list[dict[str, Any]]:
     if not file.exists():
         return []
     try:
@@ -30,13 +30,13 @@ def _read(file: Path) -> List[Dict[str, Any]]:
         return []
 
 
-def _write(file: Path, data: List[Dict[str, Any]]):
+def _write(file: Path, data: list[dict[str, Any]]):
     tmp = file.with_suffix(".tmp")
     tmp.write_text(json.dumps(data, indent=2, ensure_ascii=False), encoding="utf-8")
     shutil.move(str(tmp), str(file))
 
 
-def get_saved(username: str) -> List[Dict[str, Any]]:
+def get_saved(username: str) -> list[dict[str, Any]]:
     return _read(_get_file(username))