feat: add Jasmin assembly integration for crypto acceleration

- Integrated `zupt_mac_verify_ct` in `zupt_decrypt_buffer()` to replace C XOR loop for HMAC-SHA256
- Integrated `zupt_ct_select_32` in `zupt_mlkem768_decaps()` to replace C `cmov()` for FO transformation
- Added `include/zupt_jasmin.h` with extern declarations and ABI docs
- Added `#ifdef ZUPT_USE_JASMIN` guards with clean C fallbacks in `zupt_crypto.c` and `zupt_mlkem.c`
- Makefile now auto-detects `jasmin/*.s`, assembles and links with `-DZUPT_USE_JASMIN`

Closes #3

include/zupt_keccak.h

@@ -0,0 +1,49 @@
+/*
+ * Zupt — Backup-oriented compression with AES-256 encryption
+ * Copyright (c) 2026 Cristian Cezar Moisés
+ * SPDX-License-Identifier: MIT
+ *
+ * Keccak-f[1600] sponge: SHA3-256, SHA3-512, SHAKE-128, SHAKE-256
+ * Required by ML-KEM-768 (FIPS 203).
+ * Pure C11, zero dependencies, no dynamic allocation.
+ */
+#ifndef ZUPT_KECCAK_H
+#define ZUPT_KECCAK_H
+
+#include <stdint.h>
+#include <stddef.h>
+
+/* Sponge state: 25 × 64-bit lanes = 200 bytes */
+typedef struct {
+    uint64_t st[25];
+    uint8_t  buf[200]; /* absorption buffer */
+    size_t   rate;     /* rate in bytes */
+    size_t   pt;       /* position in buf */
+    uint8_t  dsuf;     /* domain suffix: 0x06 for SHA3, 0x1F for SHAKE */
+} zupt_keccak_ctx;
+
+/* SHA3-256: 32-byte output */
+void zupt_sha3_256(const uint8_t *data, size_t len, uint8_t out[32]);
+
+/* SHA3-512: 64-byte output */
+void zupt_sha3_512(const uint8_t *data, size_t len, uint8_t out[64]);
+
+/* SHAKE-128: extendable output */
+void zupt_shake128(const uint8_t *data, size_t dlen, uint8_t *out, size_t olen);
+
+/* SHAKE-256: extendable output */
+void zupt_shake256(const uint8_t *data, size_t dlen, uint8_t *out, size_t olen);
+
+/* Incremental SHAKE-128 for ML-KEM sampling */
+void zupt_shake128_init(zupt_keccak_ctx *ctx);
+void zupt_shake128_absorb(zupt_keccak_ctx *ctx, const uint8_t *data, size_t len);
+void zupt_shake128_finalize(zupt_keccak_ctx *ctx);
+void zupt_shake128_squeeze(zupt_keccak_ctx *ctx, uint8_t *out, size_t len);
+
+/* Incremental SHAKE-256 */
+void zupt_shake256_init(zupt_keccak_ctx *ctx);
+void zupt_shake256_absorb(zupt_keccak_ctx *ctx, const uint8_t *data, size_t len);
+void zupt_shake256_finalize(zupt_keccak_ctx *ctx);
+void zupt_shake256_squeeze(zupt_keccak_ctx *ctx, uint8_t *out, size_t len);
+
+#endif