chore(lint): apply ruff --fix (4443 auto-fixes)

Auto-fixed categories:
- F401: unused imports removed
- I001: import blocks sorted
- W293: trailing whitespace stripped
- UP035: deprecated typing imports replaced
- SIM: simplify suggestions applied
- ARG: unused args prefixed with underscore
- T201: print statements removed
- F841: unused variables removed
- RUF059: unpacked variables prefixed

Remaining ~1500 unfixable errors (C901, B904, N806, E402) require manual work.

Backend smoke tests: 13/13 passed.

backend/src/services/git/_base.py

@@ -10,14 +10,15 @@ import os
 import re
 import shutil
 from pathlib import Path
-from typing import Any, Dict, List, Optional
+
+from fastapi import HTTPException
 from git import Repo
 from git.exc import InvalidGitRepositoryError, NoSuchPathError
-from fastapi import HTTPException
-from src.core.logger import logger, belief_scope
-from src.models.git import GitRepository
-from src.models.config import AppConfigRecord
+
 from src.core.database import SessionLocal
+from src.core.logger import belief_scope, logger
+from src.models.config import AppConfigRecord
+from src.models.git import GitRepository
 
 
 # #region GitServiceBase [C:3] [TYPE Class]
@@ -94,7 +95,7 @@ class GitServiceBase:
     # @PRE: repo_key can be None/empty.
     # @POST: Returns normalized non-empty key.
     # @RETURN: str
-    def _normalize_repo_key(self, repo_key: Optional[str]) -> str:
+    def _normalize_repo_key(self, repo_key: str | None) -> str:
         raw_key = str(repo_key or "").strip().lower()
         normalized = re.sub(r"[^a-z0-9._-]+", "-", raw_key).strip("._-")
         return normalized or "dashboard"
@@ -154,7 +155,7 @@ class GitServiceBase:
     # @PRE: dashboard_id is an integer.
     # @POST: Returns DB-local_path when present, otherwise base_path/<normalized repo_key>.
     # @RETURN: str
-    def _get_repo_path(self, dashboard_id: int, repo_key: Optional[str] = None) -> str:
+    def _get_repo_path(self, dashboard_id: int, repo_key: str | None = None) -> str:
         with belief_scope("GitService._get_repo_path"):
             if dashboard_id is None:
                 raise ValueError("dashboard_id cannot be None")
@@ -199,7 +200,7 @@ class GitServiceBase:
     # @PRE: dashboard_id is int, remote_url is valid Git URL, pat is provided.
     # @POST: Repository is cloned or opened at the local path.
     # @RETURN: Repo
-    def init_repo(self, dashboard_id: int, remote_url: str, pat: str, repo_key: Optional[str] = None) -> Repo:
+    def init_repo(self, dashboard_id: int, remote_url: str, pat: str, repo_key: str | None = None) -> Repo:
         with belief_scope("GitService.init_repo"):
             self._ensure_base_path_exists()
             repo_path = self._get_repo_path(dashboard_id, repo_key=repo_key or str(dashboard_id))
@@ -269,7 +270,7 @@ class GitServiceBase:
             except Exception as e:
                 session.rollback()
                 logger.error(f"[delete_repo][Coherence:Failed] Failed to delete repository for dashboard {dashboard_id}: {e}")
-                raise HTTPException(status_code=500, detail=f"Failed to delete repository: {str(e)}")
+                raise HTTPException(status_code=500, detail=f"Failed to delete repository: {e!s}")
             finally:
                 session.close()
     # endregion delete_repo
@@ -296,7 +297,7 @@ class GitServiceBase:
     # @PURPOSE: Configure repository-local Git committer identity for user-scoped operations.
     # @PRE: dashboard_id repository exists; git_username/git_email may be empty.
     # @POST: Repository config has user.name and user.email when both identity values are provided.
-    def configure_identity(self, dashboard_id: int, git_username: Optional[str], git_email: Optional[str]) -> None:
+    def configure_identity(self, dashboard_id: int, git_username: str | None, git_email: str | None) -> None:
         with belief_scope("GitService.configure_identity"):
             normalized_username = str(git_username or "").strip()
             normalized_email = str(git_email or "").strip()
@@ -310,7 +311,7 @@ class GitServiceBase:
                 logger.reason(f"Applied repository-local git identity for dashboard {dashboard_id}", extra={"src": "configure_identity"})
             except Exception as e:
                 logger.error(f"[configure_identity][Coherence:Failed] Failed to configure git identity: {e}")
-                raise HTTPException(status_code=500, detail=f"Failed to configure git identity: {str(e)}")
+                raise HTTPException(status_code=500, detail=f"Failed to configure git identity: {e!s}")
     # endregion configure_identity
 # #endregion GitServiceBase
 # #endregion GitServiceBase