feat(oauth): import favoris/abos Google (YouTube) et Twitch vers abonnements/likes

- Backend: server/oauth.mjs (auth URL, echange code, refresh, fetch
  subscriptions/likes Google, follows Twitch), table oauth_connections
  + migration, routes /api/oauth/:provider/{url,callback,preview,import},
  /api/oauth/{status,connections}
- Front: /library/import (connect, preview, import), service
  oauth-import, lien depuis Abonnements
- Config: GOOGLE_CLIENT_ID/SECRET/REDIRECT_URI, TWITCH_REDIRECT_URI,
  OAUTH_APP_BASE_URL documentes (.env.example, docker-compose),
  passthrough docker-compose.local.yml, roadmap README cochee

src/app.routes.ts

@@ -64,6 +64,11 @@ export const APP_ROUTES: Routes = [
     loadComponent: () => import('./components/library/subscriptions/subscriptions.component').then(m => m.SubscriptionsComponent),
     title: 'NewTube - Subscriptions'
   },
+  {
+    path: 'library/import',
+    loadComponent: () => import('./components/library/import/import.component').then(m => m.ImportComponent),
+    title: 'NewTube - Import'
+  },
   {
     path: 'library/downloads/:id',
     loadComponent: () => import('./components/library/downloads/download-play.component').then(m => m.DownloadPlayComponent),