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/unittests/unittests.c

@@ -36,6 +36,7 @@
 #include "test_form.h"
 #include "test_callbacks.h"
 #include "test_plugins_disco.h"
+#include "test_database_export.h"
 
 #define muc_unit_test(f) cmocka_unit_test_setup_teardown(f, muc_before_test, muc_after_test)
 
@@ -656,6 +657,43 @@ main(int argc, char* argv[])
         cmocka_unit_test_setup_teardown(test_allow_unencrypted_message_confirms_on_second_attempt, load_preferences, close_preferences),
         cmocka_unit_test_setup_teardown(test_cmd_force_encryption_invalid_policy, load_preferences, close_preferences),
         cmocka_unit_test_setup_teardown(test_allow_unencrypted_message_invalid_mode, load_preferences, close_preferences),
+
+        // Flatfile export/import round-trip
+        cmocka_unit_test(test_ff_roundtrip_simple_chat),
+        cmocka_unit_test(test_ff_roundtrip_with_all_metadata),
+        cmocka_unit_test(test_ff_roundtrip_with_resource),
+        cmocka_unit_test(test_ff_roundtrip_newline_in_body),
+        cmocka_unit_test(test_ff_roundtrip_pipe_in_stanza_id),
+        cmocka_unit_test(test_ff_roundtrip_backslash_in_body),
+        cmocka_unit_test(test_ff_roundtrip_unicode_body),
+        cmocka_unit_test(test_ff_roundtrip_empty_body),
+        cmocka_unit_test(test_ff_roundtrip_colonspace_in_resource),
+        cmocka_unit_test(test_ff_roundtrip_muc_type),
+        cmocka_unit_test(test_ff_roundtrip_omemo_enc),
+        cmocka_unit_test(test_ff_roundtrip_replace_id),
+
+        // Escape / unescape
+        cmocka_unit_test(test_ff_escape_unescape_message_identity),
+        cmocka_unit_test(test_ff_escape_unescape_meta_identity),
+        cmocka_unit_test(test_ff_escape_meta_null_returns_null),
+        cmocka_unit_test(test_ff_escape_message_null_returns_empty),
+
+        // jid_to_dir
+        cmocka_unit_test(test_ff_jid_to_dir_simple),
+        cmocka_unit_test(test_ff_jid_to_dir_with_at),
+        cmocka_unit_test(test_ff_jid_to_dir_path_traversal_rejected),
+        cmocka_unit_test(test_ff_jid_to_dir_null),
+
+        // Parser edge cases
+        cmocka_unit_test(test_ff_parse_line_empty),
+        cmocka_unit_test(test_ff_parse_line_comment),
+        cmocka_unit_test(test_ff_parse_line_legacy_format),
+        cmocka_unit_test(test_ff_parse_line_no_metadata),
+        cmocka_unit_test(test_ff_parse_line_invalid_timestamp),
+
+        // Type/enc round-trip
+        cmocka_unit_test(test_ff_type_str_roundtrip),
+        cmocka_unit_test(test_ff_enc_str_roundtrip),
     };
     return cmocka_run_group_tests(all_tests, NULL, NULL);
 }