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>

scripts/add_i18n_module_loading.py

@@ -6,7 +6,6 @@ This ensures module translations are loaded before use.
 
 import re
 from pathlib import Path
-from collections import defaultdict
 
 PROJECT_ROOT = Path(__file__).parent.parent
 MODULES_DIR = PROJECT_ROOT / "app" / "modules"