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/src/wled_controller/api/routes/_preview_helpers.py

@@ -3,16 +3,14 @@
 import asyncio
 import base64
 import io
-import secrets
 import threading
 import time
-from typing import Callable, List, Optional
+from typing import Callable, Optional
 
 import numpy as np
 from PIL import Image
 from starlette.websockets import WebSocket
 
-from wled_controller.config import get_config
 from wled_controller.core.filters import FilterRegistry, ImagePool
 from wled_controller.utils import get_logger
 

server/src/wled_controller/api/routes/audio_templates.py

@@ -1,7 +1,6 @@
 """Audio capture template and engine routes."""
 
 import asyncio
-import json
 from fastapi import APIRouter, HTTPException, Depends, Query
 from starlette.websockets import WebSocket, WebSocketDisconnect
 

server/src/wled_controller/api/routes/color_strip_processing.py

@@ -2,10 +2,8 @@
 
 import asyncio
 import json as _json
-import time as _time
 import uuid as _uuid
 
-import numpy as np
 from fastapi import APIRouter, HTTPException, Depends, Query, WebSocket, WebSocketDisconnect
 
 from wled_controller.api.auth import AuthRequired

server/src/wled_controller/api/routes/color_strip_sources.py

@@ -32,11 +32,10 @@ from wled_controller.api.schemas.devices import (
 )
 from wled_controller.core.capture.calibration import (
     calibration_from_dict,
-    calibration_to_dict,
 )
 from wled_controller.core.capture.screen_capture import get_available_displays
 from wled_controller.core.processing.processor_manager import ProcessorManager
-from wled_controller.storage.color_strip_source import AdvancedPictureColorStripSource, ApiInputColorStripSource, CompositeColorStripSource, NotificationColorStripSource, PictureColorStripSource, ProcessedColorStripSource
+from wled_controller.storage.color_strip_source import AdvancedPictureColorStripSource, ApiInputColorStripSource, CompositeColorStripSource, NotificationColorStripSource, PictureColorStripSource
 from wled_controller.storage.color_strip_store import ColorStripStore
 from wled_controller.storage.picture_source import ProcessedPictureSource, ScreenCapturePictureSource
 from wled_controller.storage.picture_source_store import PictureSourceStore
@@ -136,7 +135,7 @@ def _extract_css_kwargs(data) -> dict:
     else:
         kwargs["calibration"] = None
     kwargs["stops"] = [s.model_dump() for s in data.stops] if data.stops is not None else None
-    kwargs["layers"] = [l.model_dump() for l in data.layers] if data.layers is not None else None
+    kwargs["layers"] = [layer.model_dump() for layer in data.layers] if data.layers is not None else None
     kwargs["zones"] = [z.model_dump() for z in data.zones] if data.zones is not None else None
     kwargs["animation"] = data.animation.model_dump() if data.animation else None
     return kwargs
@@ -870,7 +869,7 @@ async def test_color_strip_ws(
             meta["border_width"] = cal.border_width
         if is_composite and hasattr(source, "layers"):
             # Send layer info for composite preview
-            enabled_layers = [l for l in source.layers if l.get("enabled", True)]
+            enabled_layers = [layer for layer in source.layers if layer.get("enabled", True)]
             layer_infos = []  # [{name, id, is_notification, has_brightness, ...}, ...]
             for layer in enabled_layers:
                 info = {"id": layer["source_id"], "name": layer.get("source_id", "?"),

server/src/wled_controller/api/routes/devices.py

@@ -32,7 +32,6 @@ from wled_controller.core.processing.processor_manager import ProcessorManager
 from wled_controller.storage import DeviceStore
 from wled_controller.storage.output_target_store import OutputTargetStore
 from wled_controller.utils import get_logger
-from wled_controller.storage.base_store import EntityNotFoundError
 
 logger = get_logger(__name__)
 

server/src/wled_controller/api/routes/output_targets.py

@@ -3,7 +3,6 @@
 import asyncio
 
 from fastapi import APIRouter, HTTPException, Depends
-from fastapi import Query as QueryParam
 
 from wled_controller.api.auth import AuthRequired
 from wled_controller.api.dependencies import (

server/src/wled_controller/api/routes/output_targets_control.py

@@ -3,15 +3,12 @@
 Extracted from output_targets.py to keep files under 800 lines.
 """
 
-import asyncio
 
 from fastapi import APIRouter, HTTPException, Depends, Query, WebSocket, WebSocketDisconnect
 
 from wled_controller.api.auth import AuthRequired
 from wled_controller.api.dependencies import (
-    fire_entity_event,
     get_color_strip_store,
-    get_device_store,
     get_output_target_store,
     get_picture_source_store,
     get_processor_manager,

server/src/wled_controller/api/routes/output_targets_keycolors.py

@@ -306,7 +306,7 @@ async def test_kc_target_ws(
     # Load stores
     target_store_inst: OutputTargetStore = get_output_target_store()
     source_store_inst: PictureSourceStore = get_picture_source_store()
-    template_store_inst: TemplateStore = get_template_store()
+    get_template_store()
     pattern_store_inst: PatternTemplateStore = get_pattern_template_store()
     processor_manager_inst: ProcessorManager = get_processor_manager()
     device_store_inst: DeviceStore = get_device_store()

server/src/wled_controller/api/routes/system.py

@@ -55,7 +55,7 @@ logger = get_logger(__name__)
 psutil.cpu_percent(interval=None)
 
 # GPU monitoring (initialized once in utils.gpu, shared with metrics_history)
-from wled_controller.utils.gpu import nvml_available as _nvml_available, nvml as _nvml, nvml_handle as _nvml_handle
+from wled_controller.utils.gpu import nvml_available as _nvml_available, nvml as _nvml, nvml_handle as _nvml_handle  # noqa: E402
 
 
 def _get_cpu_name() -> str | None: