- UpdateParamsCommand with execute/undo for color/speed/direction/length
- Uses module-level currentShowId (not this._showId) matching existing pattern
- BlockInspector renders compact strip with animation label, color swatch,
speed input, direction select, length input, and remove button
- Color change committed on 'change' event (not 'input') to avoid command flood
- _onDelete callback wired to remove button for app.js to handle
- CommandHistory class with execute/undo/redo, 50-step max, redo-clear on new action
- PlaceBlockCommand, MoveBlockCommand, ResizeBlockCommand, DeleteBlockCommand
- setCurrentShowId() module-level function for backend sync routing
- syncBlock() fire-and-forget fetch helper for backend sync
- POST/PATCH/DELETE /api/shows/{show_id}/tracks/{device_id}/blocks endpoints
- timeline router registered in main.py with prefix=/api
