feat(processed-audio-sources): phase 5 - frontend audio processing templates

Add Audio Processing Templates management UI to Streams tab:
- Template editor modal with filter list via FilterListManager
- CardSection with reconciliation for template cards
- DataCache instances for templates and audio filter defs
- Audio filter icon mappings in filter-list.ts
- i18n keys in en/ru/zh locales

plans/processed-audio-sources/CONTEXT.md

@@ -9,7 +9,7 @@
 - **Test:** `cd server && py -3.13 -m pytest tests/ --no-cov -q`
 
 ## Current State
-Phases 1-4 implemented. Phase 4 (Runtime Integration) wired the audio filter pipeline into the stream runtime.
+Phases 1-5 implemented. Phase 5 (Frontend Templates) added UI for managing audio processing templates.
 
 Phase 1 framework:
 - `AudioFilter` base class, `AudioFilterRegistry`, `AudioFilterOptionDef` in `core/audio/filters/`
@@ -94,7 +94,7 @@ _(none yet)_
 | Phase 2 | impl-agent | — | No | All 11 filters implemented, no deviations |
 | Phase 3 | impl-agent | — | No | All 11 tasks done; channel/band logic deferred to Phase 4 |
 | Phase 4 | impl-agent | — | No | All 6 tasks done; dependency injection threaded through |
-| Phase 5 | — | — | — | — |
+| Phase 5 | impl-agent | — | No | 6/7 tasks done; Task 4 (preview) deferred to Phase 7 |
 | Phase 6 | — | — | — | — |
 | Phase 7 | — | — | — | — |