fix: use uint8_t* for SO_KEEPALIVEAUTO getter (AUD-002)

[occamsshavingkit]

Summary

Fixes type-width mismatch in the SO_KEEPALIVEAUTO socket option getter.

Problem

Ethernet/socket.c:1383 wrote the keepalive auto value through uint16_t*:

*(uint16_t*) arg = getSn_KPALVTR(sn);

But the setter at socket.c:1334 and the documented type at socket.h:583 both use uint8_t. A conforming caller passing uint8_t value has one adjacent byte overwritten and may trigger an unaligned halfword fault on strict-alignment MCUs.

Fix

Change uint16_t* to uint8_t*:

*(uint8_t*) arg = getSn_KPALVTR(sn);

Verification

• Multi-chip compile check: passes for all 7 _WIZCHIP_ values
• ASan/UBSan: canary test confirms exactly 1 byte written, adjacent bytes intact