Add chat.sune signing key to assetlinks

Keep the legacy com.planetrenox.sune entry so the old app stays
fullscreen, and add the new chat.sune package with its new key.
Ignore keystore files so signing keys can never be committed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

public/.well-known/assetlinks.json

@@ -8,5 +8,15 @@
         "E8:7D:70:60:C2:7D:EF:CB:4D:4D:2B:E2:2E:5E:37:ED:F7:0B:1E:F5:77:D7:04:1F:6B:07:EC:B8:1D:78:6D:43"
       ]
     }
+  },
+  {
+    "relation": ["delegate_permission/common.handle_all_urls"],
+    "target": {
+      "namespace": "android_app",
+      "package_name": "chat.sune",
+      "sha256_cert_fingerprints": [
+        "09:85:1F:7B:BB:40:67:9C:F8:70:1C:7D:9F:65:72:77:78:0E:C0:58:CF:34:09:9A:97:D2:8A:74:FB:CE:87:2A"
+      ]
+    }
   }
 ]