fix: resolve all 153 ruff lint errors for CI

Auto-fixed 138 unused imports and f-string issues. Manually fixed:
ambiguous variable names (l→layer), availability-check imports using
importlib.util.find_spec, unused Color import, ImagePool forward ref
via TYPE_CHECKING, multi-statement semicolons, and E402 suppression.

server/tests/core/test_automation_engine.py

@@ -1,8 +1,7 @@
 """Tests for AutomationEngine — condition evaluation in isolation."""
 
-import asyncio
 from datetime import datetime, timezone
-from unittest.mock import AsyncMock, MagicMock, patch
+from unittest.mock import MagicMock, patch
 
 import pytest
 
@@ -12,7 +11,6 @@ from wled_controller.storage.automation import (
     ApplicationCondition,
     Automation,
     DisplayStateCondition,
-    MQTTCondition,
     StartupCondition,
     SystemIdleCondition,
     TimeOfDayCondition,

server/tests/core/test_sync_clock_runtime.py

@@ -3,7 +3,6 @@
 import threading
 import time
 
-import pytest
 
 from wled_controller.core.processing.sync_clock_runtime import SyncClockRuntime