fix(ui,db): harden NULL handling, fix CWE-134, optimize iterations

security(CWE-134): fix format string injections + add CI check
fix(ui): subwindow lifecycle, newwin/newpad guards, fallback timestamps
fix(db): sqlite cleanup on failures, sqlite3_close_v2
fix(xmpp): queued_messages loop, barejid leak
perf(core): g_hash_table_iter_init instead of g_hash_table_get_keys
refactor(ui): CLAMP macro in _check_subwin_width
test: XEP-0012 and XEP-0045 functional tests

Author: jabber.developer2
Closes #58, #85

tests/functionaltests/test_lastactivity.h

@@ -0,0 +1,7 @@
+/*
+ * test_lastactivity.h
+ * Header for Last Activity tests (XEP-0012)
+ */
+
+void responds_to_last_activity_request(void **state);
+void last_activity_request_to_contact(void **state);