fix: protect critical re-export imports from linter removal

Problem:
- Ruff removed 'from app.core.database import Base' from models/database/base.py
- Import appeared "unused" (F401) but was actually a critical re-export
- Caused ImportError: cannot import name 'Base' at runtime
- Re-export pattern: import in one file to export from package

Solution:
1. Added F401 ignore for models/database/base.py in pyproject.toml
2. Created scripts/verify_critical_imports.py verification script
3. Integrated verification into make check and CI pipeline
4. Updated documentation with explanation

New Verification Script:
- Checks all critical re-export imports exist
- Detects import variations (parentheses, 'as' clauses)
- Handles SQLAlchemy declarative_base alternatives
- Runs as part of make check automatically

Protected Files:
- models/database/base.py - Re-exports Base for all models
- models/__init__.py - Exports Base for Alembic
- models/database/__init__.py - Exports Base from package
- All __init__.py files (already protected)

Makefile Changes:
- make verify-imports - Run import verification
- make check - Now includes verify-imports
- make ci - Includes verify-imports in pipeline

Documentation Updated:
- Code quality guide explains re-export protection
- Pre-commit workflow includes verification
- Examples of why re-exports matter

This prevents future issues where linters remove seemingly
"unused" imports that are actually critical for application structure.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Makefile

@@ -190,9 +190,13 @@ lint-strict:
 	@echo "Type checking with mypy..."
 	$(PYTHON) -m mypy .
 
-check: format lint
+check: format lint verify-imports
 
-ci: lint-strict test-coverage
+ci: lint-strict verify-imports test-coverage
+
+verify-imports:
+	@echo "Verifying critical imports..."
+	$(PYTHON) scripts/verify_critical_imports.py
 
 qa: format lint test-coverage docs-check
 	@echo "Quality assurance checks completed!"
@@ -333,7 +337,8 @@ help:
 	@echo "  format               - Format code with ruff"
 	@echo "  lint                 - Lint and auto-fix with ruff + mypy"
 	@echo "  lint-strict          - Lint without auto-fix + mypy"
-	@echo "  check                - Format + lint"
+	@echo "  verify-imports       - Verify critical imports haven't been removed"
+	@echo "  check                - Format + lint + verify imports"
 	@echo "  ci                   - Full CI pipeline (strict)"
 	@echo "  qa                   - Quality assurance"
 	@echo ""