fix: address all remaining review warnings and style issues

- config.h: bump PROTOCOL_VERSION from "1.2.0" to "1.3.0" (WARNING-1)
- client_cli.c: fix realloc leak on exclude/include patterns (WARNING-2)
- file.c: document sendfile fallback as safety net only (WARNING-4)
- metadata.c: add warning log for utimensat failure (WARNING-5/STYLE-1)
- utils.c: fix is_dir_in_manifest false prefix match (WARNING-1)
- utils.c: fix double rmdir on recursive collapse, add errno.h (WARNING-2)
- client_send.c: guard unchecked send calls for manifest/finished (WARNING-3)
- client_send.c: send STATUS_NEXT on rc==2 without delta (WARNING-4)

src/shared/config.h

@@ -42,7 +42,7 @@ typedef struct Config {
   char* tls_ca;
 } Config;
 
-#define PROTOCOL_VERSION "1.2.0"
+#define PROTOCOL_VERSION "1.3.0"
 #define DEFAULT_CHUNK_SIZE (10 * 1024 * 1024)
 
 Config* config_create(char* version, char* send_directory, char* receive_directory,