feat(native): app link verification files for the native app

/.well-known/apple-app-site-association (team HXAUF476A7, bundle
com.al-arcade.el3ab: /t/ and /r/ links open the app) and assetlinks.json
(package com.alarcade.el3ab; the debug key for now, the release and Play
signing keys join once known).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.well-known/.htaccess

+# App link verification files (the native app, docs in root/el3ab-mobile).
+<Files "apple-app-site-association">
+    ForceType application/json
+</Files>

.well-known/apple-app-site-association

+{
+  "applinks": {
+    "details": [
+      { "appIDs": ["HXAUF476A7.com.al-arcade.el3ab"], "components": [ { "/": "/t/*" }, { "/": "/r/*" } ] }
+    ]
+  },
+  "webcredentials": { "apps": ["HXAUF476A7.com.al-arcade.el3ab"] }
+}

.well-known/assetlinks.json

+[
+  {
+    "relation": ["delegate_permission/common.handle_all_urls"],
+    "target": {
+      "namespace": "android_app",
+      "package_name": "com.alarcade.el3ab",
+      "sha256_cert_fingerprints": [
+        "00:A4:FE:AB:A1:75:BA:66:B2:DA:5B:E8:65:9D:50:AF:C2:A6:8E:2F:10:DD:0D:65:7F:63:17:9F:8B:EA:48:60"
+      ]
+    }
+  }
+]