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_accuracy.py

@@ -22,8 +22,6 @@ import time
 import numpy as np
 import pytest
 
-pytestmark = [pytest.mark.integration]
-
 from gps_denied.core.benchmark import (
     AccuracyBenchmark,
     BenchmarkResult,
@@ -33,6 +31,8 @@ from gps_denied.core.benchmark import (
 from gps_denied.schemas import GPSPoint
 from gps_denied.schemas.eskf import ESKFConfig
 
+pytestmark = [pytest.mark.integration]
+
 ORIGIN = GPSPoint(lat=49.0, lon=32.0)