Lockdown PIN redaction, a build guard, and favorite compaction (#11285)

* Redact the pairing PIN from unauthorized lockdown clients

* Fail the build when PacketAPI would bypass the lockdown gate

* Compact kept favorites when resetting the node database

* Make the compaction loop reference const

src/mesh/NodeDB.cpp

@@ -1607,15 +1607,19 @@ void NodeDB::resetNodes(bool keepFavorites)
     numMeshNodes = 1;
     if (keepFavorites) {
         LOG_INFO("Clearing node database - preserving favorites");
-        for (size_t i = 0; i < meshNodes->size(); i++) {
-            meshtastic_NodeInfoLite &node = meshNodes->at(i);
-            if (i > 0 && !nodeInfoLiteIsFavorite(&node)) {
-                eraseNodeSatellites(node.num);
-                node = meshtastic_NodeInfoLite();
-            } else {
+        // Compact favorites into contiguous low slots: zeroing in place leaves one above
+        // numMeshNodes, invisible to every `i < numMeshNodes` scan yet still serialized to flash.
+        for (size_t i = 1; i < meshNodes->size(); i++) {
+            const meshtastic_NodeInfoLite &node = meshNodes->at(i);
+            if (nodeInfoLiteIsFavorite(&node)) {
+                if (numMeshNodes != i)
+                    meshNodes->at(numMeshNodes) = node;
                 numMeshNodes += 1;
+            } else if (node.num) {
+                eraseNodeSatellites(node.num);
             }
-        };
+        }
+        std::fill(nodeDatabase.nodes.begin() + numMeshNodes, nodeDatabase.nodes.end(), meshtastic_NodeInfoLite());
     } else {
         LOG_INFO("Clearing node database - removing favorites");
         for (size_t i = 1; i < meshNodes->size(); i++) {

src/mesh/PhoneAPI.cpp

@@ -767,6 +767,12 @@ size_t PhoneAPI::getFromRadio(uint8_t *buf)
             LOG_DEBUG("Send config: bluetooth");
             fromRadioScratch.config.which_payload_variant = meshtastic_Config_bluetooth_tag;
             fromRadioScratch.config.payload_variant.bluetooth = config.bluetooth;
+#ifdef MESHTASTIC_PHONEAPI_ACCESS_CONTROL
+            if (!getAdminAuthorized()) {
+                // The pairing PIN is a shared secret; never expose it to an unauthenticated client.
+                fromRadioScratch.config.payload_variant.bluetooth.fixed_pin = 0;
+            }
+#endif
             break;
         case meshtastic_Config_security_tag:
             LOG_DEBUG("Send config: security");

src/mesh/api/PacketAPI.cpp

@@ -6,6 +6,12 @@
 #include "RadioInterface.h"
 #include "modules/NodeInfoModule.h"
 
+#ifdef MESHTASTIC_PHONEAPI_ACCESS_CONTROL
+// receivePacket() dispatches ToRadio straight to MeshService, bypassing handleToRadioPacket and so
+// the lockdown admin gate. Fail the build rather than silently ship an admin-auth bypass.
+#error "USE_PACKET_API is incompatible with MESHTASTIC_PHONEAPI_ACCESS_CONTROL (PacketAPI bypasses the lockdown admin gate)"
+#endif
+
 PacketAPI *packetAPI = nullptr;
 
 PacketAPI *PacketAPI::create(PacketServer *_server)