fix(core)!: enforce strict C89 compliance

BREAKING CHANGE: Public API now uses unsigned char instead of uint8_t

- Remove stdint.h dependency (C99 feature, not C89, I am a fucking idiot)
- Replace uint8_t with unsigned char throughout codebase
- Affects stk_init() return type and internal functions
- Corrects unintended C99 dependency, restoring intended C89 compliance

src/stk.c

@@ -1,7 +1,6 @@
 #include "stk.h"
 #include "platform.h"
 #include "stk_log.h"
-#include <stdint.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -16,7 +15,7 @@ extern char (*stk_module_ids)[STK_MOD_ID_BUFFER];
 
 extern size_t module_count;
 
-uint8_t stk_initialized = 0;
+unsigned char stk_initialized = 0;
 
 static char stk_mod_dir[STK_PATH_MAX_OS] = "mods";
 static char stk_tmp_name[STK_MOD_ID_BUFFER] = ".tmp";
@@ -30,18 +29,18 @@ void platform_directory_watch_stop(void *handle);
 stk_module_event_t *platform_directory_watch_check(
     void *handle, char (**file_list)[STK_PATH_MAX], size_t *out_count,
     char (*loaded_module_ids)[STK_MOD_ID_BUFFER], const size_t loaded_count);
-uint8_t platform_mkdir(const char *path);
-uint8_t platform_copy_file(const char *from, const char *to);
-uint8_t platform_remove_dir(const char *path);
+unsigned char platform_mkdir(const char *path);
+unsigned char platform_copy_file(const char *from, const char *to);
+unsigned char platform_remove_dir(const char *path);
 
 void extract_module_id(const char *path, char *out_id);
 int is_mod_loaded(const char *module_id);
 
 size_t stk_module_count(void);
-uint8_t stk_module_load(const char *path, int index);
-uint8_t stk_module_load_init(const char *path, int index);
-uint8_t stk_module_init_memory(size_t capacity);
-uint8_t stk_module_realloc_memory(size_t new_capacity);
+unsigned char stk_module_load(const char *path, int index);
+unsigned char stk_module_load_init(const char *path, int index);
+unsigned char stk_module_init_memory(size_t capacity);
+unsigned char stk_module_realloc_memory(size_t new_capacity);
 void stk_module_unload(size_t index);
 void stk_module_unload_all(void);
 
@@ -70,7 +69,7 @@ static const char *stk_error_string(int error_code)
 	}
 }
 
-uint8_t stk_init(void)
+unsigned char stk_init(void)
 {
 	char (*files)[STK_PATH_MAX] = NULL;
 	size_t file_count, i, successful_loads = 0;