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

src-tauri/Cargo.toml

@@ -27,6 +27,7 @@ rusqlite = { version = "0.32", features = ["bundled"] }
 r2d2 = "0.8"
 r2d2_sqlite = "0.25"
 sqlite-vec = "=0.1.9"
+hnsw_rs = "0.3.4"
 image = { version = "0.25", default-features = false, features = ["jpeg", "png", "webp", "gif", "bmp", "tiff"] }
 fast_image_resize = { version = "6.0.0", features = ["image"] }
 walkdir = "2"
@@ -38,9 +39,63 @@ anyhow = "1"
 log = "0.4"
 ffmpeg-sidecar = "2.5.0"
 xxhash-rust = { version = "0.8", features = ["xxh3"] }
+memmap2 = "0.9"
 sysinfo = "0.38.4"
 candle-core = { version = "0.10.2", features = ["cuda"] }
 candle-nn = { version = "0.10.2", features = ["cuda"] }
 candle-transformers = { version = "0.10.2", features = ["cuda"] }
 hf-hub = { version = "0.5.0", default-features = false, features = ["ureq", "native-tls"] }
 tokenizers = "0.22.1"
+ort = { version = "2.0.0-rc.12", default-features = false, features = ["std", "ndarray", "download-binaries", "copy-dylibs", "load-dynamic", "directml", "api-24", "tls-native"] }
+ureq = { version = "3.3.0", default-features = false, features = ["native-tls"] }
+zip = { version = "4.6.1", default-features = false, features = ["deflate"] }
+csv = "1"
+tauri-plugin-notification = "2"
+
+# ── Dev-mode performance ────────────────────────────────────────────────────
+# opt-level=1 on the main crate keeps incremental compile short.
+# Only the packages that are genuine hot-path bottlenecks in dev get opt-level=3
+# (using "*" caused cargo to recheck all dependency fingerprints too aggressively,
+# which caused spurious full rebuilds and linker conflicts).
+[profile.dev]
+opt-level = 1
+
+# ML inference — without opt these run 20-50× slower than release
+[profile.dev.package.candle-core]
+opt-level = 3
+[profile.dev.package.candle-nn]
+opt-level = 3
+[profile.dev.package.candle-transformers]
+opt-level = 3
+
+# ONNX runtime (WD tagger)
+[profile.dev.package.ort]
+opt-level = 3
+[profile.dev.package.ort-sys]
+opt-level = 3
+
+# Image decode/resize workers
+[profile.dev.package.image]
+opt-level = 3
+[profile.dev.package.fast_image_resize]
+opt-level = 3
+
+# Parallel work scheduler
+[profile.dev.package.rayon]
+opt-level = 3
+[profile.dev.package.rayon-core]
+opt-level = 3
+
+# Tokenisation (embedding model pre-processing)
+[profile.dev.package.tokenizers]
+opt-level = 3
+
+# Hashing (duplicate finder)
+[profile.dev.package.xxhash-rust]
+opt-level = 3
+
+# SQLite (frequent db calls in workers)
+[profile.dev.package.rusqlite]
+opt-level = 3
+[profile.dev.package.libsqlite3-sys]
+opt-level = 3