refactor(core,lib): move all core and lib structs and constants to a separate header file

lib/database.c

@@ -3,6 +3,7 @@
 #include <sys/stat.h>
 #include <time.h>
 
+#include "../include/core_func.h"
 #include "../include/tanabata.h"
 
 int tanabata_init(Tanabata *tanabata) {

lib/kazari.c

@@ -1,5 +1,6 @@
 #include <malloc.h>
 
+#include "../include/core_func.h"
 #include "../include/tanabata.h"
 
 int tanabata_kazari_add(Tanabata *tanabata, uint64_t sasa_id, uint64_t tanzaku_id) {

lib/sasa.c

@@ -1,6 +1,7 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include "../include/core_func.h"
 #include "../include/tanabata.h"
 
 int tanabata_sasa_add(Tanabata *tanabata, const char *path) {

lib/tanzaku.c

@@ -1,5 +1,6 @@
 #include <string.h>
 
+#include "../include/core_func.h"
 #include "../include/tanabata.h"
 
 int tanabata_tanzaku_add(Tanabata *tanabata, const char *name, const char *description) {