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_vo.py

@@ -3,8 +3,6 @@
 import numpy as np
 import pytest
 
-pytestmark = [pytest.mark.unit]
-
 from gps_denied.core.models import ModelManager
 from gps_denied.core.vo import (
     CuVSLAMVisualOdometry,
@@ -16,6 +14,8 @@ from gps_denied.core.vo import (
 from gps_denied.schemas import CameraParameters
 from gps_denied.schemas.vo import Features, Matches
 
+pytestmark = [pytest.mark.unit]
+
 
 @pytest.fixture
 def vo():