feat(include/common): add thread‑safe logging macros and error handling

- New Features
  - Wrap log output with flockfile/funlockfile to guarantee atomic writes.
  - Add LOG_PERROR macro to report messages with errno details.
- Enhancements
  - Include <errno.h> and <string.h> for robust error handling.
  - Remove unused errorf declaration.
- Bug Fixes
  - None.

include/common/log.h

@@ -3,6 +3,8 @@
 
 #include <stdio.h>
 #include <time.h>
+#include <errno.h>
+#include <string.h>
 
 // Assuming g_verbose is defined globally or we pass it
 extern int g_verbose;
@@ -15,15 +17,18 @@ extern int is_daemon;
 
 #define LOG_MACRO(level, prefix, out_stream, ...) do { \
     if (level == LOG_LEVEL_DEBUG && !g_verbose) break; \
+    flockfile(out_stream); \
     fprintf(out_stream, "[VBX-%s] ", prefix); \
     fprintf(out_stream, __VA_ARGS__); \
     fprintf(out_stream, "\n"); \
     fflush(out_stream); \
+    funlockfile(out_stream); \
 } while(0)
 
 #define LOG_DEBUG(...)  LOG_MACRO(LOG_LEVEL_DEBUG, "DEBUG", stdout, __VA_ARGS__)
 #define LOG_INFO(...)   LOG_MACRO(LOG_LEVEL_INFO,  "INFO",  stdout, __VA_ARGS__)
 #define LOG_WARN(...)   LOG_MACRO(LOG_LEVEL_WARN,  "WARN",  stderr, __VA_ARGS__)
 #define LOG_ERROR(...)  LOG_MACRO(LOG_LEVEL_ERROR, "ERROR", stderr, __VA_ARGS__)
+#define LOG_PERROR(msg) LOG_MACRO(LOG_LEVEL_ERROR, "ERROR", stderr, "%s: %s", msg, strerror(errno))
 
 #endif // VBX_LOG_H

include/common/utils.h

@@ -8,10 +8,6 @@
 // Returns 1 on success, 0 on truncation/error
 int safe_snprintf(char *dst, size_t dst_sz, const char *fmt, ...);
 
-// fprintf to stderr with printf-style formatting. Returns 1 for convenient
-// `return errorf(...)` usage.
-int errorf(const char *fmt, ...);
-
 // Common runtime helpers
 const char *get_runtime_dir(void);
 void build_pidfile_path(char *buffer, size_t buflen);