Bug fixes applied:
1. poly1305_update buffer path: Added missing h[0..3] data addition
2. poly1305_update full block: Fixed hibit from 2^40 to 2^128 (1ULL << 24)
3. poly1305_final (64-bit): Output full 128-bit MAC instead of 64-bit
Remaining issues:
- ESP32 version of poly1305_final still outputs only 64-bit MAC
- poly1305_final for partial blocks may have issues
- RFC 7539 test still fails (MAC is all zeros)
WireGuard tests: 28 passed, 4 failed
km