Add repo filters, UI tabs and dev docs

Enhance UI and dev workflow: add main/right tabbed panels (Repositories/Local and Clone/Settings/Servers), repository owner filter pills (All/Personal/Organizations), org-grouped listing, repo cards, git output and empty-state styling. Introduce new state vars (activeMainTab, activeRightTab, repoOwnerFilter, currentUserLogin) and update event bindings to toggle tabs/filters and focus appropriate panels on actions. Add fetchCurrentUser to gitea-api and use it when loading repositories to distinguish personal vs organization repos (falls back to mock user on error). Update README with development/prerequisites and build instructions and rename npm script "tauri:dev" -> "dev" for running the Tauri dev process.

package.json

@@ -5,7 +5,7 @@
   "type": "module",
   "scripts": {
     "tauri": "tauri",
-    "tauri:dev": "tauri dev",
+    "dev": "tauri dev",
     "tauri:build": "tauri build"
   },
   "devDependencies": {