fix(userland): Fix 'clear' command, backspace keycodes (0x7F/0x08), serial keyboard input & make run target

- Add 'clear' and 'cls' builtin handlers in LazyBox shell
- Output ANSI \033[2J\033[H sequence on tty_clear() to clear serial/UART terminals
- Support both ASCII 0x7F (DEL) and 0x08 (BS) for Backspace in shell and nano editor
- Connect 16550 serial input to keyboard_get_key() on x86_64 for headless terminals
- Add ANSI escape sequence decoding for arrow keys (Up/Down/Left/Right/Home/End/Del)
- Update Makefile 'make run' and 'make qemu' with -display none for smooth terminal execution
- Add 'make run-gui' target for optional graphical SDL/GTK window

Makefile

@@ -53,7 +53,7 @@ ifeq ($(ARCH), x86_64)
     TARGET        = $(IMAGE)
     QEMU_CMD      = qemu-system-x86_64 -drive format=raw,file=$(IMAGE) \
                     -netdev user,id=net0,hostfwd=tcp::2222-:22,hostfwd=tcp::8080-:80 \
-                    -device e1000,netdev=net0 -serial stdio
+                    -device e1000,netdev=net0 -serial stdio -display none
 
 else ifneq ($(filter $(ARCH), aarch64 arm64),)
     CROSS_COMPILE ?= aarch64-linux-gnu-
@@ -375,6 +375,17 @@ $(IMAGE): $(BUILD_DIR)/boot/boot.bin $(BUILD_DIR)/boot/stage2.bin $(BUILD_DIR)/k
 run qemu: $(TARGET)
 	$(QEMU_CMD)
 
+run-gui: $(TARGET)
+ifeq ($(ARCH), x86_64)
+	qemu-system-x86_64 -drive format=raw,file=$(IMAGE) \
+		-netdev user,id=net0,hostfwd=tcp::2222-:22,hostfwd=tcp::8080-:80 \
+		-device e1000,netdev=net0 -serial stdio
+else ifneq ($(filter $(ARCH), aarch64 arm64),)
+	qemu-system-aarch64 -M virt -cpu cortex-a57 -m 128M -kernel $(BUILD_DIR)/kernel.elf -serial stdio
+else
+	qemu-system-arm -M virt -cpu cortex-a15 -m 128M -kernel $(BUILD_DIR)/kernel.elf -serial stdio
+endif
+
 run-server: $(IMAGE)
 	qemu-system-x86_64 -drive format=raw,file=$(IMAGE) \
 		-netdev user,id=net0,hostfwd=tcp::2222-:22,hostfwd=tcp::8080-:80 \