TutorialVault: complete Tauri v2 port with runtime fixes

Rename from TutorialDock to TutorialVault. Remove legacy Python app
and scripts. Fix video playback, subtitles, metadata display, window
state persistence, and auto-download of ffmpeg/ffprobe on first run.
Bundle fonts via npm instead of runtime download.

package.json

@@ -1,5 +1,5 @@
 {
-  "name": "tutorialdock",
+  "name": "tutorialvault",
   "private": true,
   "version": "0.1.0",
   "type": "module",
@@ -9,6 +9,10 @@
     "tauri": "tauri"
   },
   "dependencies": {
+    "@fontsource/ibm-plex-mono": "^5.2.7",
+    "@fontsource/manrope": "^5.2.8",
+    "@fontsource/sora": "^5.2.8",
+    "@fortawesome/fontawesome-free": "^7.2.0",
     "@tauri-apps/api": "^2.0.0"
   },
   "devDependencies": {