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/models/git.py

@@ -1,11 +1,14 @@
 # #region GitModels [TYPE Module] [SEMANTICS sqlalchemy, git, model, config, sync]
 
 import enum
-from datetime import datetime
-from sqlalchemy import Column, String, Integer, DateTime, Enum, ForeignKey, Boolean
 import uuid
+from datetime import datetime
+
+from sqlalchemy import Boolean, Column, DateTime, Enum, ForeignKey, Integer, String
+
 from src.core.database import Base
 
+
 class GitProvider(str, enum.Enum):
     GITHUB = "GITHUB"
     GITLAB = "GITLAB"