sched: Implement basic scheduling and signal handling system

Note: this is probably 25% broken, but it works right now as written, so I hope it all works.

- Added a new scheduler header file (scheduler.h) defining task structures, scheduling policies, and signal handling mechanisms.
- Integrated scheduling functions into the syscall interface, including SYS_GETPID, SYS_GETPPID, SYS_EXIT, SYS_SCHED_YIELD, SYS_NICE, SYS_KILL, SYS_SIGACTION, SYS_SIGPROCMASK, SYS_SCHED_GETSCHEDULER, and SYS_SCHED_SETSCHEDULER.
- Updated syscall handler to manage new scheduling-related syscalls and signal actions.

Signed-off-by: kaguya <vpshinomiya@protonmail.com>

src/main.c

@@ -31,6 +31,7 @@
 #include "arch/x86_64/sys/apic.h"
 #include "arch/x86_64/sys/ioapic.h"
 #include "drivers/input/ps2.h"
+#include "sched/scheduler.h"
 
 
 uintptr_t g_hhdm_offset;
@@ -128,7 +129,7 @@ static uacpi_interrupt_ret handle_power_button(uacpi_handle ctx) {
 
 
 void kmain(void) {
-    if (LIMINE_BASE_REVISION_SUPPORTED(limine_base_revision) == false) {
+    if (LIMINE_BASE_REVISION_SUPPORTED(limine_base_revision) == false) { 
         hcf();
     }
 
@@ -350,8 +351,19 @@ void kmain(void) {
 
 
     syscall_init();
+
+    sched_init();
+
     start_userspace();
 
+    sched_yield();
+
+
+    for (;;) {
+        sched_yield();
+    }
+
     // We're done, just hang...
-    hcf();
-}
+    //hcf();
+}
+