fix(lint): resolve all ruff E402/I001/F821 errors

- Move pytestmark after all imports in 35 test files (E402: not-at-top)
- Add TYPE_CHECKING guard for FlightProcessor in composition.py (F821)
- Sort import blocks in src/ and tests/ (I001 auto-fix via ruff --fix)
- ruff check src/ tests/ now exits 0 with no errors

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

tests/test_database.py

@@ -1,15 +1,14 @@
 """Tests for the database layer — CRUD, cascade, transactions."""
 
 import pytest
-
-pytestmark = [pytest.mark.integration]
-
 from sqlalchemy import event
 from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
 
 from gps_denied.db.models import Base
 from gps_denied.db.repository import FlightRepository
 
+pytestmark = [pytest.mark.integration]
+
 
 @pytest.fixture
 async def session():