Adds snapshot system to Helix Stadium:
Backend:
- Snapshot data model (8 slots per preset, captures block bypass
+ params + master volume)
- Snapshot API endpoints: list, save, recall, rename, delete
- Integrated into preset serialization/deserialization
- Tracks current_snapshot in state / WebSocket broadcasts
Frontend:
- Camera icon in header bar with current snapshot number
- SnapshotPanel as slide-up overlay
- 8 snapshot slots in a horizontal row
- Tap to recall filled snapshot, tap empty slot to save
- Press-and-hold (600ms) to save current state
- Inline name editing on tap
- Discard Edits toggle
- Green flash indicator on save
- Delete button for active snapshot
- New Preset button: finds first empty slot, saves with default name
- Looper/Recorder tab: Record/Stop via arecord backend, list captures, play back
- Rig: shows loaded IR name more clearly + quick-link buttons to browse IRs/Models
- Backend: capture/start, capture/stop, captures API endpoints with file serve
- Status bar: CPU load + sample rate from /api/state, TUNER badge shown immediately
- Rig: optimistic toggle updates (bypass/tuner respond instantly), prominent tuner card
- FX Chain: loads real block params from /api/block-params/{fx_type}, Add Block picker with all FX types
- Record: replaced fake multitrack with real Signal Monitor (live I/O VU, clip detect, level history)
- Backend: added _gather_system_stats() returning cpu_percent and sample_rate
- Added input_level and output_level to /api/state (scaled 0-100)
- React RigScreen now reads real levels from state instead of random walk
- When no audio flows, VU meters show flat (0) instead of fake animation
- New dark UI with 7 tabs: Rig, FX Chain, Models, IRs, Presets, Settings, Record
- All screens wired to live API endpoints
- Real-time state via WebSocket + polling fallback
- Models screen: list/load/unload/upload NAM files + Tone3000 search/install
- IRs screen: list/load/unload/upload IR files + Tone3000 search/install
- Presets screen: browse banks, activate, save, delete
- Settings screen: WiFi scan/connect/hotspot, Bluetooth/MIDI, 4CM routing
- Rig screen: live state, volume, bypass, tuner, signal chain
- FX Chain screen: block params, per-block bypass
- Serves at / instead of /ui
- Built with Vite, ~71KB gzipped
shawn