refactor(service): harden KMP service layer — database init, connection reliability, handler decomposition (#4992)

core/model/src/commonMain/kotlin/org/meshtastic/core/model/RadioController.kt

@@ -56,11 +56,15 @@ interface RadioController {
     suspend fun favoriteNode(nodeNum: Int)
 
     /**
-     * Sends our shared contact information (identity and public key) to a remote node.
+     * Sends our shared contact information (identity and public key) to the firmware's NodeDB.
+     *
+     * This ensures the firmware has the correct public key for the destination node before a PKI-encrypted direct
+     * message is sent. The method suspends until the radio acknowledges the admin packet.
      *
      * @param nodeNum The destination node number.
+     * @return `true` if the radio accepted the contact, `false` on timeout or failure.
      */
-    suspend fun sendSharedContact(nodeNum: Int)
+    suspend fun sendSharedContact(nodeNum: Int): Boolean
 
     /**
      * Updates the local radio configuration.

core/model/src/commonMain/kotlin/org/meshtastic/core/model/service/ServiceAction.kt

@@ -16,6 +16,7 @@
  */
 package org.meshtastic.core.model.service
 
+import kotlinx.coroutines.CompletableDeferred
 import org.meshtastic.core.model.Node
 import org.meshtastic.proto.SharedContact
 
@@ -32,5 +33,17 @@ sealed class ServiceAction {
 
     data class ImportContact(val contact: SharedContact) : ServiceAction()
 
-    data class SendContact(val contact: SharedContact) : ServiceAction()
+    /**
+     * Sends a shared contact (identity + public key) to the firmware's NodeDB.
+     *
+     * The [result] deferred is completed with `true` when the radio acknowledges the admin packet, or `false` on
+     * timeout/failure. Callers that need to guarantee the contact is stored before sending a subsequent DM should
+     * `await()` this deferred.
+     *
+     * Not a data class: [result] is a [CompletableDeferred] with identity-based equality that would break data class
+     * equals/hashCode/copy semantics.
+     */
+    class SendContact(val contact: SharedContact) : ServiceAction() {
+        val result: CompletableDeferred<Boolean> = CompletableDeferred()
+    }
 }