fix(calls): ship LiveKit fallback in Element Call config

Well-known fetch fails CORS on IPv4 (Wix redirect), so the embedded
widget needs the JWT service URL in its own config.json.

apps/web/res/element-call-config.json

@@ -0,0 +1,10 @@
+{
+    "matrix_rtc_session": {
+        "wait_for_key_rotation_ms": 5000,
+        "delayed_leave_event_restart_ms": 4000,
+        "delayed_leave_event_delay_ms": 18000
+    },
+    "livekit": {
+        "livekit_service_url": "https://matrix.healthchat.ch/livekit-jwt-service"
+    }
+}

apps/web/webpack.config.ts

@@ -728,6 +728,18 @@ export default (env: string, argv: Record<string, any>): webpack.Configuration =
                         context: path.join(getPackageRoot("@element-hq/element-call-embedded"), "dist"),
                         to: path.join(__dirname, "webapp", "widgets", "element-call"),
                     },
+                    // HealthChat: overwrite the embedded Element Call config with one that carries a
+                    // LiveKit fallback. Element Call fetches https://healthchat.ch/.well-known/matrix/client
+                    // itself from the widget origin; over IPv4 that host is served by Wix, which answers
+                    // a 301 to matrix.healthchat.ch without an Access-Control-Allow-Origin header, so
+                    // the fetch fails CORS on IPv4-only networks and Element Call falls back to this
+                    // file. Without the livekit block it errors with MISSING_MATRIX_RTC_TRANSPORT.
+                    // Keep the matrix_rtc_session timers in sync with what the package ships.
+                    {
+                        from: "res/element-call-config.json",
+                        to: path.join(__dirname, "webapp", "widgets", "element-call", "config.json"),
+                        force: true,
+                    },
                     // Mobile guide assets
                     {
                         from: "assets/**",