feat: add fullscreen QR code for subscription connection

- New ConnectionQR page with fullscreen QR display (no modal)
- QR button in InstallationGuide header next to platform selector
- Respects hideLink setting: shows URL below QR only when visible
- i18n translations for ru, en, zh, fa

package.json

@@ -44,6 +44,7 @@
     "i18next": "^25.8.4",
     "i18next-browser-languagedetector": "^8.2.0",
     "jsencrypt": "^3.5.4",
+    "qrcode.react": "^4.2.0",
     "react": "^19.2.4",
     "react-dom": "^19.2.4",
     "react-i18next": "^16.5.4",