Add functional and unit tests for DB export/import

- 2 functional tests: export_sqlite_to_flatfile, import_flatfile_to_sqlite
  with XEP-0203 delay timestamps for deterministic verification
- 27 unit tests for database_export covering edge cases
- Merge test/db-functional-tests: 12 DB persistence tests (test_history)
- Group 2 rebalanced: 25 tests (23 base + 2 SQLite-only export/import)
- #ifdef HAVE_SQLITE guards for export/import tests
- prof_stop() helper in proftest.c
- Makefile.am: source ordering cleanup, new test files added

tests/functionaltests/functionaltests.c

@@ -16,7 +16,7 @@
  *
  * Tests are organized into groups for better maintainability and parallel execution:
  *   Group 1: Connect, Ping, Rooms, Software, Last Activity  (19 tests)
- *   Group 2: Message, Receipts, Roster, DB History           (22 tests)
+ *   Group 2: Message, Receipts, Roster, DB History           (23+2 tests, +2 with SQLite)
  *   Group 3: Chat Session, Presence, Disconnect              (22 tests)
  *   Group 4: MUC, Carbons                                    (21 tests)
  *
@@ -54,6 +54,9 @@
 #include "test_disconnect.h"
 #include "test_lastactivity.h"
 #include "test_history.h"
+#ifdef HAVE_SQLITE
+#include "test_export_import.h"
+#endif
 
 /* Macro to wrap each test with setup/teardown functions */
 #define PROF_FUNC_TEST(test) cmocka_unit_test_setup_teardown(test, init_prof_test, close_prof_test)
@@ -116,9 +119,15 @@ main(int argc, char* argv[])
     /* ============================================================
      * GROUP 2: Message, Receipts, Roster, DB History
      * Core messaging and contact management
-     * (23 tests)
+     * (25 tests with SQLite, 23 without)
      * ============================================================ */
     const struct CMUnitTest group2_tests[] = {
+#ifdef HAVE_SQLITE
+        /* Export/Import — cross-backend migration (SQLite ↔ flat-file) */
+        PROF_FUNC_TEST(export_sqlite_to_flatfile),
+        PROF_FUNC_TEST(import_flatfile_to_sqlite),
+#endif
+
         /* Basic message send/receive */
         PROF_FUNC_TEST(message_send),
         PROF_FUNC_TEST(message_receive_console),
@@ -147,9 +156,7 @@ main(int argc, char* argv[])
         PROF_FUNC_TEST(message_db_history_long_message),
         PROF_FUNC_TEST(message_db_history_newline),
         PROF_FUNC_TEST(message_db_history_service_chars),
-#ifdef HAVE_HISTORY_VERIFY
         PROF_FUNC_TEST(message_db_history_verify),
-#endif
         PROF_FUNC_TEST(message_db_history_lmc),
     };