fix: reformat codebase and fix const-correctness for CI lint

- Reformat all C/H files to match .clang-format (LLVM style)
- Fix 26 cppcheck const-correctness warnings (constParameterPointer,
  constVariablePointer, constVariable)
- Update function declarations in headers to match const parameters

src/shared/chunk.h

@@ -10,15 +10,15 @@
 #define DESIRED_CHUNK_SIZE (10 * 1024 * 1024)
 
 typedef struct {
-  File **items;
+  File** items;
   int element_count;
 } Chunk;
 
-Chunk *chunk_create(File **items, int element_count);
-void chunk_destroy(void *chunk);
-Data *chunk_serialize(Chunk *chunk, bool use_metadata);
-Chunk *chunk_deserialize(Data *data, bool use_metadata);
-Data *chunk_compress(Chunk *chunk, int compression_level, bool use_metadata);
-Chunk *receive_chunk_data(int fd, Config *config);
+Chunk* chunk_create(File** items, int element_count);
+void chunk_destroy(void* chunk);
+Data* chunk_serialize(Chunk* chunk, bool use_metadata);
+Chunk* chunk_deserialize(Data* data, bool use_metadata);
+Data* chunk_compress(Chunk* chunk, int compression_level, bool use_metadata);
+Chunk* receive_chunk_data(int fd, const Config* config);
 
 #endif