Moves common asset operation methods (upsertAssets, removeAssets,
updateAssetOperation) from TimelineManager into PhotostreamManager
base class, making them available to all photostream implementations.
Updates all consuming components to use the more accurate 'upsertAssets'
naming instead of separate 'addAssets' and 'updateAssets' methods.
- Move asset operation methods to PhotostreamManager base class
- Replace addAssets/updateAssets calls with unified upsertAssets method
- Update type imports to use PhotostreamManager instead of TimelineManager
- Remove operations-support.svelte.ts (functionality moved to base class)
- Add abstract upsertAssetIntoSegment method for subclass customization
- Extracted asset viewer navigation and action handling logic from Timeline.svelte into a dedicated TimelineAssetViewer component
- Reduces Timeline.svelte complexity by ~150 lines and improves separation of concerns
- No functional changes - purely a refactoring to improve code organization
## Changes
- Created new TimelineAssetViewer.svelte component containing all asset viewer-related logic
- Moved handlePrevious, handleNext, handleRandom, handleClose, handlePreAction, and handleAction methods
- Timeline.svelte now only passes required props to the new component
- Maintained all existing functionality including navigation, asset actions, and stack management
midzelis