Initial commit — Tauri image gallery with sqlite-vec

Sets up Tauri v2 + React frontend with SQLite metadata store,
sqlite-vec for CLIP embedding infrastructure, and r2d2 connection
pool replacing the single Arc<Mutex<Connection>>. Indexer now uses
rayon for parallel file metadata collection.

src-tauri/capabilities/default.json

@@ -0,0 +1,17 @@
+{
+  "$schema": "../gen/schemas/desktop-schema.json",
+  "identifier": "default",
+  "description": "Capability for the main window",
+  "windows": ["main"],
+  "permissions": [
+    "core:default",
+    "opener:default",
+    "dialog:default",
+    "dialog:allow-open",
+    "fs:default",
+    "fs:allow-read-file",
+    "fs:allow-read-dir",
+    "fs:read-files",
+    "fs:read-dirs"
+  ]
+}