Fix kernel warnings and memory-safety issues

[pradosh-arduino]

Motivation

• Reduce a large class of compiler warnings and eliminate obvious memory-safety problems discovered while building the kernel under strict warning flags.
• Make APIs and headers strictly prototyped to satisfy -Wstrict-prototypes and related pedantic checks.
• Prevent duplicated header-owned storage and uninitialized DMA/bounce-buffer use that could lead to crashes or UB.

Description

• Move AHCI per-port storage out of the header by changing static ahci_port_mem_t port_mem[32]; to extern in includes/ahci.h and define ahci_port_mem_t port_mem[32]; once in kernel/C/ahci.c to avoid duplicate definitions and unused-variable warnings.
• Harden DMA and temporary-buffer handling by initializing DMA pointers to NULL, only copying from DMA buffers on successful operations, and guarding frees in ahci.c/nvme.c/gpt.c/mbr.c to avoid uninitialized use and double-free/copy-on-failure paths.
• Add missing standard headers and prototypes (<string.h>/<memory.h>, strdup, memcpy usages) and convert many no-argument function declarations/definitions to strict prototypes (void) across headers and C files to fix -Wstrict-prototypes and missing-prototype diagnostics.
• Fix varargs/ promotion bugs and integer-width/sign issues by adjusting va_arg types in debugger.c, providing a local 64-bit-to-hex helper, and adding explicit casts/unsigned suffixes where arithmetic could change sign/width (AHCI/NVMe/TSS/GDT/paging/etc.).
• Fix packed-member access in acpi.c by copying the acpi_gas before using it and mark OEM string const to avoid discarded-qualifiers.
• Add small API cleanups and missing declarations (e.g. remove_mount, list_all_mounts, io_wait_us/io_wait_ms) and add a non-executable .note.GNU-stack section to the syscall ASM to silence linker executable-stack warnings.

Testing

• Ran a full build (make -C source) which completes and links wing_kernel.elf successfully after the changes.
• Performed iterative strict-warning builds using the requested CFLAGS/-Wall -Wextra -Wpedantic ... -Werror and triaged/fixed many issues; the strict build was run repeatedly and the majority of warnings were eliminated but one remaining strict-blocker was observed in kernel/C/image/targa.c (narrowing/prototype issues) and left for a follow-up.
• Ran git diff --check and a pre-commit check and committed the changes (commit present) with the working-tree passing the make invocation used for CI above.

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Codex Task