Run precious tidy --all with clang-format 21

Reformat to match clang-format 21.1.8 output. The only change is
indentation of preprocessor directives inside #ifdef/#ifndef blocks.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: oschwald

src/data-pool.c

@@ -1,5 +1,5 @@
 #ifndef _POSIX_C_SOURCE
-#define _POSIX_C_SOURCE 200809L
+    #define _POSIX_C_SOURCE 200809L
 #endif
 
 #include "data-pool.h"
@@ -146,8 +146,8 @@ MMDB_entry_data_list_s *data_pool_to_list(MMDB_data_pool_s *const pool) {
 
 #ifdef TEST_DATA_POOL
 
-#include <libtap/tap.h>
-#include <maxminddb_test_helper.h>
+    #include <libtap/tap.h>
+    #include <maxminddb_test_helper.h>
 
 static void test_can_multiply(void);