etcp: replace connections linked-list with indexed ll_queue, add state/ref_count lifecycle

- Remove ETCP_CONN.next linked-list, UTUN_INSTANCE.connections list/count
- Unified connections in single ll_queue indexed by peer_node_id (0=pending)
- struct conn_queue_entry { peer_node_id, conn* } for uniform queue data
- Connection lifecycle via etcp.c: create→pending, conn_ready→indexed, close→detach+deferred free
- Close split: phase1 detach from external world, phase2 deferred via uasync_call_soon
- etcp_conn_set_peer_node_id: reindex on ID change (WARN)
- etcp_conn_ref_take/free: blocking close until refcount returns to 0
- Remove chat_connections — use unified connections queue directly
- Update all iteration/search patterns across 40 files (src + tests + chatgui)

src/control_server.c

@@ -885,10 +885,10 @@ static void send_conn_list(struct control_server* server, struct control_client*
     
     /* Count connections */
     uint8_t count = 0;
-    struct ETCP_CONN* conn = instance->connections;
-    while (conn && count < ETCPMON_MAX_CONNECTIONS) {
+    struct ll_entry* entry = instance->connections->head;
+    while (entry && count < ETCPMON_MAX_CONNECTIONS) {
         count++;
-        conn = conn->next;
+        entry = entry->next;
     }
     
     /* Build response */
@@ -909,12 +909,13 @@ static void send_conn_list(struct control_server* server, struct control_client*
     rsp->count = count;
     
     struct etcpmon_conn_info* info = (struct etcpmon_conn_info*)(buffer + sizeof(*hdr) + sizeof(*rsp));
-    conn = instance->connections;
-    for (uint8_t i = 0; i < count && conn; i++) {
-        info[i].peer_node_id = conn->peer_node_id;
-        strncpy(info[i].name, conn->log_name, ETCPMON_MAX_CONN_NAME - 1);
+    entry = instance->connections->head;
+    for (uint8_t i = 0; i < count && entry; i++) {
+        struct conn_queue_entry* ce = (struct conn_queue_entry*)entry->data;
+        info[i].peer_node_id = ce->conn->peer_node_id;
+        strncpy(info[i].name, ce->conn->log_name, ETCPMON_MAX_CONN_NAME - 1);
         info[i].name[ETCPMON_MAX_CONN_NAME - 1] = '\0';
-        conn = conn->next;
+        entry = entry->next;
     }
     
     /* Log and send response */
@@ -1372,14 +1373,11 @@ static void send_debug_config(struct control_server* server, struct control_clie
 
 static struct ETCP_CONN* find_connection_by_peer_id(struct UTUN_INSTANCE* instance, 
                                                      uint64_t peer_id) {
-    struct ETCP_CONN* conn = instance->connections;
-    while (conn) {
-        if (conn->peer_node_id == peer_id) {
-            return conn;
-        }
-        conn = conn->next;
-    }
-    return NULL;
+    if (!instance || !instance->connections) return NULL;
+    struct ll_entry* e = queue_find_data_by_index(instance->connections, (const uint8_t*)&peer_id);
+    if (!e) return NULL;
+    struct conn_queue_entry* ce = (struct conn_queue_entry*)e->data;
+    return ce->conn;
 }
 
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