Fix kernel warning audit issues

[pradosh-arduino]

Motivation

• The project switched from permissive warnings to -Wall/pedantic builds which exposed many real bugs and dangerous casts across kernel subsystems.
• The change set aims to aggressively address high-confidence warning-identified defects while preserving existing kernel architecture and public APIs.
• Fixes focus on I/O helpers, interrupt setup, device probing, input handling, ELF/FWDE loading, and several API/signature mismatches that could cause undefined behavior.

Description

• ACPI: corrected OnesOp handling to use UINT64_MAX, constrained SLP type bitshifts, added explicit I/O port casts, and fixed PM1 status wait precedence to (inw(...) & 1U) == 0U. (source/kernel/C/acpi-shutdown.c)
• PS/2 mouse & keyboard: made internal helpers static, replaced non-standard binary literals with portable masks, stored packets as uint8_t, fixed signed/unsigned movement math and framebuffer clamping, and synced PIT tick types with consumers. (source/kernel/C/user-input/ps2-mouse.c, source/kernel/C/user-input/keyboard.c, source/kernel/C/pit.c)
• PCI / PCI-ID: removed dangling stack-returned strings by using static buffers and cstring returns, fixed AHCI BAR masking and pointer casts, widened GPU name storage and deferred GPU-global pointer assignment until stable storage exists. (source/kernel/C/pci_id.c, source/kernel/C/pci.c, source/includes/pci.h, source/includes/pci_id.h)
• ELF / FWDE / IDT: hardened ELF handling for additional FS enums and zero-initialized headers, expanded FWDE signature field and made verify_signature const-correct, fixed IDT pointer initialization and narrowed offset writes before lidt. (source/kernel/C/executables/elf.c, source/includes/executables/fwde.h, source/kernel/C/executables/fwde.c, source/kernel/C/interrupts/idt.c)
• Miscellaneous API and correctness fixes: made print_bitmap accept const bool*, fixed strlen/string prototypes and itoa visibility, tightened RTC I/O casts and BCD conversions, adjusted logging/ISR prototypes and added missing prototypes for MSR helpers, and cleaned up unused/implicit prototypes across many headers. (multiple source/includes/* and source/kernel/C/* files)

Testing

• Ran the default build with cd source && make which completed and linked wing_kernel.elf successfully (build artifacts present and linker step finished). (Succeeded)
• Ran a strict warning-as-error build using the full audit CFLAGS (-Wall -Wextra -Wpedantic -Wshadow -Wconversion -Wsign-conversion -Wcast-align -Wcast-qual -Wstrict-prototypes -Wmissing-prototypes -Wpointer-arith -Wwrite-strings -Wundef -Wformat=2 -Wswitch-enum -Werror ...) which still fails due to remaining FAT16/filesystem-related strict warnings; those areas were left for targeted manual review. (Failed — remaining issues in fat16.c and a few other modules)

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Codex Task