cleanup: remove duplicate native OS drop listener from LibraryPanel; Canvas is canonical drop target

feat: LibraryPanel - OS drag-drop import, library-to-canvas drag, inline tag/metadata editor with proper UX

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fix: listen for board://image_added event to actually show captured images on canvas, add Upload File button to library"

fix: LibraryPanel - proper useEffect loading, tag add/remove via Rust, refresh on open, delete from library

refactor: LibraryPanel + SettingsPanel + BrowserPanel with Tauri integration

Remove old SolidJS frontend files (replaced by React prototype UI)

Fix Shield popover airspace and add Phase 3 library board core