v0.3.0: keyboard culling, toasts+undo, smart chips, selection gestures, guide

- keyboard-first culling in the library grid: cursor nav (arrows), 1-5 rating,
  P/X pick/reject labels, [ ] cycle color, Space preview, Delete trash
- toast + in-app confirm/prompt overlays replace all native alert/confirm/prompt;
  delete is now Gmail-style deferred trash with Undo
- smart quick-filter chips (today / this week / this year / best 4+ / videos),
  backed by a new mtime date-range filter in AssetQuery
- selection gestures: shift-click range, Ctrl/Cmd+A select-all, Esc clear
- mosaic: grid lines, lower default density/blend, click tile to view source
- user guide updated: library, culling, shortcuts, search/map/groups, mosaic

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "ai-photo-organizer",
-  "version": "0.2.0",
+  "version": "0.3.0",
   "description": "Local-first AI photo organizer — face recognition + EXIF based auto archiving",
   "author": "PhotoAI",
   "license": "MIT",