0.3.8 — plugins install from the catalog only (no auto-install)

Drop first-run auto-install. New plugins are discovered and installed by hand
from Settings → Plugins, which now shows an 'Available to install' catalog
fetched from the Gitea plugin registry (with loading / offline-retry states).

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

src-tauri/tauri.conf.json

@@ -2,7 +2,7 @@
   "$schema": "https://schema.tauri.app/config/2",
   "productName": "Exbyte Depot",
   "mainBinaryName": "Exbyte Depot",
-  "version": "0.3.7",
+  "version": "0.3.8",
   "identifier": "com.bonchellon.exbyte-depot",
   "build": {
     "beforeDevCommand": "npm run dev",