fix(lint): auto-fix ruff violations and tune lint rules

- Auto-fixed 4,496 lint issues (import sorting, modern syntax, etc.)
- Added ignore rules for patterns intentional in this codebase:
  E402 (late imports), E712 (SQLAlchemy filters), B904 (raise from),
  SIM108/SIM105/SIM117 (readability preferences)
- Added per-file ignores for tests and scripts
- Excluded broken scripts/rename_terminology.py (has curly quotes)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/modules/billing/dependencies/feature_gate.py

@@ -37,7 +37,7 @@ Usage:
 import asyncio
 import functools
 import logging
-from typing import Callable
+from collections.abc import Callable
 
 from fastapi import Depends, HTTPException
 from sqlalchemy.orm import Session
@@ -106,7 +106,7 @@ class RequireFeature:
 
         for feature_code in self.feature_codes:
             if feature_service.has_feature_for_store(db, store_id, feature_code):
-                return None
+                return
 
         # None of the features are available
         feature_code = self.feature_codes[0]
@@ -204,8 +204,7 @@ def require_feature(*feature_codes: str) -> Callable:
 
         if asyncio.iscoroutinefunction(func):
             return async_wrapper
-        else:
-            return sync_wrapper
+        return sync_wrapper
 
     return decorator