feat(deeplink): point deeplinks at HealthChat hosts

Claims app.healthchat.ch and to.healthchat.ch as App Links, registers the
healthchat:// scheme, and drops the unreachable mobile.element.io handling.

appconfig/src/main/kotlin/io/element/android/appconfig/MatrixConfiguration.kt

@@ -10,5 +10,19 @@ package io.element.android.appconfig
 
 object MatrixConfiguration {
     const val MATRIX_TO_PERMALINK_BASE_URL: String = "https://matrix.to/#/"
+
+    /**
+     * HealthChat's own matrix.to deployment (https://github.com/Novaloop-AG/healthchat-matrix.to).
+     * It uses the exact same URL format as matrix.to, so links can be translated by swapping the
+     * base URL. Used both to recognise incoming links and to build links shared outside of Matrix.
+     */
+    const val HEALTHCHAT_TO_PERMALINK_BASE_URL: String = "https://to.healthchat.ch/#/"
+
+    /**
+     * Base URL of the HealthChat web client, which is what the healthchat:// custom scheme
+     * handed out by [HEALTHCHAT_TO_PERMALINK_BASE_URL] points to.
+     */
+    const val HEALTHCHAT_WEB_BASE_URL: String = "https://app.healthchat.ch/#/"
+
     val clientPermalinkBaseUrl: String? = null
 }