feat(arch): Add AArch64 / ARMv8i CPU support, cross-compilation & Linux Kconfig TUI

- Implement AArch64 HAL, vector table (16 aligned vectors), GICv2, Generic Timer, Stage-1 MMU (39-bit VA), PL011 UART
- Build unified multi-architecture abstraction layer in include/arch/arch.h
- Create interactive Linux-like Kconfig TUI menuconfig in scripts/kconfig/menuconfig.py
- Support make menuconfig, defconfig, x86_64_defconfig, aarch64_defconfig
- Update master Makefile for cross-compiling x86_64 (x86_64-elf-) and AArch64 (aarch64-linux-gnu-)
- Dynamic architecture awareness across printk, uname, neofetch, and LazyBox

include/init/version.h

@@ -5,9 +5,20 @@
 #define SUBOS_VERSION_MINOR 2
 #define SUBOS_VERSION_PATCH 0
 #define SUBOS_VERSION_CODENAME "Titan"
+
+#if defined(__x86_64__)
 #define SUBOS_VERSION_STRING "0.2.0-lts (x86_64)"
 #define SUBOS_BUILD_TARGET "x86_64-elf-baremetal"
-#define SUBOS_COMPILER "x86_64-elf-gcc (Modular Monolithic)"
+#define SUBOS_COMPILER "x86_64-elf-gcc"
+#elif defined(__aarch64__)
+#define SUBOS_VERSION_STRING "0.2.0-lts (aarch64)"
+#define SUBOS_BUILD_TARGET "aarch64-linux-gnu-baremetal"
+#define SUBOS_COMPILER "aarch64-linux-gnu-gcc"
+#else
+#define SUBOS_VERSION_STRING "0.2.0-lts (generic)"
+#define SUBOS_BUILD_TARGET "generic-elf-baremetal"
+#define SUBOS_COMPILER "gcc"
+#endif
 
 const char* kernel_get_version(void);
 const char* kernel_get_build_banner(void);