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/xmpp/form.c

@@ -437,18 +437,7 @@ form_get_form_type_field(DataForm* form)
 gboolean
 form_tag_exists(DataForm* form, const char* const tag)
 {
-    GList* tags = g_hash_table_get_keys(form->tag_to_var);
-    GList* curr = tags;
-    while (curr) {
-        if (g_strcmp0(curr->data, tag) == 0) {
-            g_list_free(tags);
-            return TRUE;
-        }
-        curr = g_list_next(curr);
-    }
-
-    g_list_free(tags);
-    return FALSE;
+    return g_hash_table_contains(form->tag_to_var, tag);
 }
 
 form_field_type_t