refactor: optimize hash table iterations and fix security issues #58

- refactor(core): replace g_hash_table_get_keys with g_hash_table_iter_init
  * Eliminates temporary GList allocations
  * Improves iteration performance
  * Affected: connection.c, cmd_defs.c, cmd_funcs.c, omemo.c, gpg.c,
    disco.c, form.c, autocompleters.c, capabilities.c, callbacks.c

- fix(xmpp): correct queued_messages loop in connection.c:1031
  * Remove incorrect NULL check that prevented message storage
  * calloc zeros array, causing loop to skip immediately
  * Fixes dropped messages during reconnection with SM enabled

- fix(ui): prevent format string vulnerabilities in cons_show calls
  * Replace cons_show(variable) with cons_show("%s", variable)
  * Protects against format string attacks if variables contain %
  * Updated instances across cmd_funcs.c, connection.c, ox.c,
    console.c, core.c

src/plugins/callbacks.c

@@ -149,15 +149,14 @@ callbacks_remove(const char* const plugin_name)
 {
     GHashTable* command_hash = g_hash_table_lookup(p_commands, plugin_name);
     if (command_hash) {
-        GList* commands = g_hash_table_get_keys(command_hash);
-        GList* curr = commands;
-        while (curr) {
-            char* command = curr->data;
+        GHashTableIter iter;
+        gpointer key, value;
+        g_hash_table_iter_init(&iter, command_hash);
+        while (g_hash_table_iter_next(&iter, &key, &value)) {
+            char* command = (char*)key;
             cmd_ac_remove(command);
             cmd_ac_remove_help(&command[1]);
-            curr = g_list_next(curr);
         }
-        g_list_free(commands);
     }
 
     g_hash_table_remove(p_commands, plugin_name);
@@ -165,13 +164,12 @@ callbacks_remove(const char* const plugin_name)
 
     GHashTable* tag_to_win_cb_hash = g_hash_table_lookup(p_window_callbacks, plugin_name);
     if (tag_to_win_cb_hash) {
-        GList* tags = g_hash_table_get_keys(tag_to_win_cb_hash);
-        GList* curr = tags;
-        while (curr) {
-            wins_close_plugin(curr->data);
-            curr = g_list_next(curr);
+        GHashTableIter iter;
+        gpointer key, value;
+        g_hash_table_iter_init(&iter, tag_to_win_cb_hash);
+        while (g_hash_table_iter_next(&iter, &key, &value)) {
+            wins_close_plugin(key);
         }
-        g_list_free(tags);
     }
 
     g_hash_table_remove(p_window_callbacks, plugin_name);