feat(android): QR pairing — scan, deep link, one-step auto-login

Companion side of docs/companion-pairing-qr.md (v1 contract):
- Connect screen lands on Scan Node's QR / Enter Manually; NESMenu gains
  an add-server-by-QR icon button
- QrScannerOverlay: CameraX + ZXing core (pinned, on-device, no ML Kit)
- ServerQrParser: archipelago://pair?v=1&url=..[&pw=..]; unknown major v
  -> 'update the app'; upsert by origin so re-scans never duplicate
- archipelago:// deep link registered (singleTask + onNewIntent) for the
  modal's 'Open in companion app' button
- WebView auto-fills and submits Login.vue's password form when a stored
  password exists — demo QR is one step to a logged-in session
- Web modal + handoff doc copy synced to the real label: Scan Node's QR
- v0.4.13 (versionCode 17)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Android/app/src/main/AndroidManifest.xml

@@ -4,6 +4,9 @@
 
     <uses-permission android:name="android.permission.INTERNET" />
     <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
+    <!-- Pairing-QR scanner. Camera is optional: manual entry still works without one. -->
+    <uses-permission android:name="android.permission.CAMERA" />
+    <uses-feature android:name="android.hardware.camera.any" android:required="false" />
 
     <application
         android:name=".ArchipelagoApp"
@@ -19,6 +22,7 @@
         <activity
             android:name=".MainActivity"
             android:exported="true"
+            android:launchMode="singleTask"
             android:theme="@style/Theme.Archipelago.Splash"
             android:windowSoftInputMode="adjustResize"
             android:configChanges="orientation|screenSize|screenLayout|keyboardHidden">
@@ -26,6 +30,14 @@
                 <action android:name="android.intent.action.MAIN" />
                 <category android:name="android.intent.category.LAUNCHER" />
             </intent-filter>
+            <!-- Pairing deep link from the web UI's Companion popup:
+                 archipelago://pair?v=1&url=...[&pw=...] (docs/companion-pairing-qr.md) -->
+            <intent-filter>
+                <action android:name="android.intent.action.VIEW" />
+                <category android:name="android.intent.category.DEFAULT" />
+                <category android:name="android.intent.category.BROWSABLE" />
+                <data android:scheme="archipelago" android:host="pair" />
+            </intent-filter>
         </activity>
     </application>