feat(discovery): AI tagging, semantic search, similarity, duplicate finder, folder management

Adds a full discovery and organisation layer to the gallery.

## AI Tagger
- WD tagger (ONNX via ort) with DirectML/CPU acceleration
- Per-image and per-folder tag queuing; configurable batch size and
  confidence threshold; model downloaded on first use via ureq/zip
- Tags stored with source ('ai' | 'user'); user tags are never
  overwritten by AI; AI tags protected from accidental promotion
- Tagger pause/resume per folder; in-flight batches discarded cleanly
  on pause or cancellation without leaving jobs stuck in processing

## Semantic & Tag Search
- CLIP text-query embedding via candle (HuggingFace hub model)
- Progressive candidate doubling with filter post-processing so
  folder/rating/media-kind filters do not silently under-return results
- Tag search with DB-backed pagination (offset + COUNT total)
- Filename search unchanged; prefix syntax: s:, t:, f: in search bar

## Similarity Search
- HNSW in-memory index (hnsw_rs) with monotonic embedding_revision
  counter for cache invalidation; build_index retries if a concurrent
  write advances the revision during construction
- Folder-scoped similar search uses brute-force cosine scan (no k limit)
- Region-based similarity: crop an arbitrary rectangle in the lightbox,
  embed it with CLIP, find the nearest images globally or within folder
- Pagination for both similar and region results; scope toggle
  (all media / current folder) re-runs the query without reopening image

## Duplicate Finder
- Three-phase detection: stat (size) → sample hash (4×16 KB windows)
  → full-file hash (xxh3, large files only) to eliminate false positives
- Filesystem-first deletion: only removes DB rows for files successfully
  deleted from disk; failed files remain visible for retry
- Persisted scan cache (SQLite) with invalidation on reindex and deletion;
  both global and per-folder scopes invalidated after any deletion

## Tag Cloud & Explore
- Visual cluster explore: k-means over CLIP embeddings, configurable k,
  representative thumbnail per cluster; cache keyed on xxh3 of embedding set
- Tag explore: ranked tag list with image counts and representative
  thumbnail per tag; invalidated when AI tagging completes or folder removed
- Tag autocomplete for search bar

## Folder Management
- Inline rename (display name only, not OS rename)
- Relocate: file-picker to update folder path; all image paths rewritten
  using SUBSTR prefix replacement to avoid corrupting paths that contain
  the folder name as a substring
- Missing-folder recovery banner: Locate or Remove, never silent deletion
- Right-click context menu on sidebar items: Reindex, Rename, Locate,
  Remove; hover buttons preserved alongside context menu

## Background Tasks
- Per-folder progress panel with embedding, tagging, caption, and
  thumbnail stage breakdown
- Retry button per task for failed embeddings and tagging jobs
- Completed-task notifications (system tray via tauri-plugin-notification)
- Scan errors shown inline; WalkDir permission errors protect existing
  records from deletion rather than cascading data loss

## Backend correctness
- sqlite-vec DML performed outside transactions throughout (virtual-table
  limitation); embedding revision incremented on delete as well as insert
- Tagging job discard checks status = 'processing' so paused jobs reset
  to 'pending' are also skipped, not just cancelled ones
- Stale async responses in Lightbox guarded with cancellation flags and
  currentImageIdRef for both tag-load and tag-add callbacks
- Duplicate cache cleared on reindex; folder-removal clears vector rows
  outside transaction before deleting the folder row

package.json

@@ -4,8 +4,10 @@
   "version": "0.1.0",
   "type": "module",
   "scripts": {
-    "dev": "vite",
-    "build": "tsc && vite build",
+    "build:app": "tauri build",
+    "build:vite": "tsc && vite build",
+    "dev:app": "tauri dev",
+    "dev:vite": "vite",
     "preview": "vite preview",
     "tauri": "tauri"
   },
@@ -14,7 +16,9 @@
     "@tauri-apps/api": "^2",
     "@tauri-apps/plugin-dialog": "^2.7.0",
     "@tauri-apps/plugin-fs": "^2.5.0",
+    "@tauri-apps/plugin-notification": "^2.3.3",
     "@tauri-apps/plugin-opener": "^2",
+    "d3-force": "^3.0.0",
     "framer-motion": "^12.38.0",
     "react": "^19.1.0",
     "react-dom": "^19.1.0",
@@ -23,6 +27,7 @@
   "devDependencies": {
     "@tailwindcss/vite": "^4.2.2",
     "@tauri-apps/cli": "^2",
+    "@types/d3-force": "^3.0.10",
     "@types/react": "^19.1.8",
     "@types/react-dom": "^19.1.6",
     "@vitejs/plugin-react": "^4.6.0",