Add reusable DataCache class, unify frontend cache patterns
- Create DataCache class with fetch deduplication, invalidation, subscribers
- Instantiate 10 cache instances in state.js (streams, templates, sources, etc.)
- Replace inline fetch+parse+set patterns with cache.fetch() calls across modules
- Eliminate dual _scenesCache/_presetsCache sync via shared scenePresetsCache
- Remove 9 now-unused setter functions from state.js
- Clean up unused setter imports from audio-sources, value-sources, displays
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
alexei.dolgolyov
a34edf9650