Bump to v2.0.0 — cross-platform Tauri rewrite

Major version bump reflecting the architecture change from PySide6/Qt
to Tauri v2 + Svelte 5 with cross-platform support for Windows,
macOS, and Linux.

Key changes since v1.4.0:
- Tauri v2 native desktop shell replacing PySide6/Qt
- Svelte 5 reactive frontend
- Headless Python backend as a downloadable sidecar
- Deepgram cloud transcription (managed + BYOK)
- Gitea CI/CD with per-OS builds and automated releases
- Sidecar auto-update checking on startup
- 63-test suite (Python + Svelte + Rust)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

package.json

@@ -1,7 +1,7 @@
 {
   "name": "local-transcription",
   "private": true,
-  "version": "1.4.21",
+  "version": "2.0.0",
   "type": "module",
   "scripts": {
     "dev": "vite dev",