merge: resolve dev (quality refactor) into security-fixes

- file.c split layout retained; security-hardened secure-fs helpers
  (open_secure_parent/to_disk_secure/rename_secure/stat_secure) now live in
  file.c with file_ prefix and are shared with file_receive.c
- file_receive.c takes the security branch's bounded allocations
  (receive_data_limited, data_decompress_limited, size checks) and
  STATUS_ERROR signaling
- file_send.c gains the data consistency check on file->data
- client_validation.c: stricter --tls requiring --ca, log_message style
- utils.c: hardened openat/mkdirat mkdir_r from security branch

src/shared/chunk.c

@@ -24,7 +24,7 @@ Chunk* chunk_create(File** items, int element_count) {
     return NULL;
   Chunk* chunk = (Chunk*)malloc(sizeof(Chunk));
   if (chunk == NULL) {
-    perror("ERROR: Could not allocate memory for chunk structure");
+    log_perror("ERROR: Could not allocate memory for chunk structure");
     return NULL;
   }
 
@@ -160,7 +160,7 @@ Chunk* chunk_deserialize(Data* data, bool use_metadata) {
     }
     char* path = malloc(path_len + 1);
     if (path == NULL) {
-      perror("Could not allocate memory for file path");
+      log_perror("Could not allocate memory for file path");
       array_list_delete(files);
       return NULL;
     }
@@ -247,7 +247,7 @@ Chunk* chunk_deserialize(Data* data, bool use_metadata) {
     size_t allocation_size = file_data_size > 0 ? file_data_size : 1;
     void* file_data = malloc(allocation_size);
     if (file_data == NULL) {
-      perror("Could not allocate memory for file data");
+      log_perror("Could not allocate memory for file data");
       file_destroy(file);
       array_list_delete(files);
       return NULL;