Add CSPT entity, processed CSS source type, reverse filter, and UI improvements

- Add Color Strip Processing Template (CSPT) entity: reusable filter chains
  for 1D LED strip postprocessing (backend, storage, API, frontend CRUD)
- Add "processed" color strip source type that wraps another CSS source and
  applies a CSPT filter chain (dataclass, stream, schema, modal, cards)
- Add Reverse filter for strip LED order reversal
- Add CSPT and processed CSS nodes/edges to visual graph editor
- Add CSPT test preview WS endpoint with input source selection
- Add device settings CSPT template selector (add + edit modals with hints)
- Use icon grids for palette quantization preset selector in filter lists
- Use EntitySelect for template references and test modal source selectors
- Fix filters.css_filter_template.desc missing localization
- Fix icon grid cell height inequality (grid-auto-rows: 1fr)
- Rename "Processed" subtab to "Processing Templates"
- Localize all new strings (en/ru/zh)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

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

@@ -1,5 +1,7 @@
 """Audio device routes: enumerate available audio devices."""
 
+import asyncio
+
 from fastapi import APIRouter
 
 from wled_controller.api.auth import AuthRequired
@@ -17,8 +19,12 @@ async def list_audio_devices(_auth: AuthRequired):
     filter by the selected audio template's engine type.
     """
     try:
-        devices = AudioCaptureManager.enumerate_devices()
-        by_engine = AudioCaptureManager.enumerate_devices_by_engine()
+        devices, by_engine = await asyncio.to_thread(
+            lambda: (
+                AudioCaptureManager.enumerate_devices(),
+                AudioCaptureManager.enumerate_devices_by_engine(),
+            )
+        )
         return {
             "devices": devices,
             "count": len(devices),