v0.7.0: pure C core + Zephyr module

- Extract all decode/decrypt into a dependency-free C99 core
 (include/victronble.h, src/victronble_core.c): victronble_decode(),
 is_product_adv/key_matches pre-filters, NAN sentinels, LE accessors.
- AES-128-CTR behind a hook: weak-symbol bundled tiny-AES default,
 runtime override (victronble_set_aes_ctr) for PSA/mbedTLS/hardware.
- Arduino VictronBLE class becomes a thin wrapper over the core
 (registry + nonce dedup + rate limit); public C++ API unchanged,
 NAN converted back to the legacy 0 convention.
- Host test vectors (tests/vectors): openssl-generated ciphertext,
 independent of the bundled AES; all five payload shapes + negatives.
- Zephyr module: zephyr/module.yml + Kconfig (CONFIG_VICTRONBLE) +
 observer backend (victronble_zephyr.{h,c}) — scan cb pre-filters and
 queues, dedicated decode thread, listener callbacks, slow passive
 scan defaults, stats counters. docs/ZEPHYR_PORT.md records the plan.
- library.properties: fix URL (gitea, not the nonexistent GitHub).

src/victronble_aes_sw.c

@@ -0,0 +1,38 @@
+/**
+ * victronble — bundled software AES-128-CTR backend.
+ *
+ * Weak symbol: an alternative backend (PSA Crypto, mbedTLS, hardware) defines
+ * victronble_aes_ctr_default strong and the linker drops this file's code —
+ * and with it the bundled AES tables — from the final image.
+ *
+ * Copyright (c) 2025-2026 Scott Penrose
+ * License: MIT
+ */
+
+#include "victronble.h"
+#include "crypto/vble_aes.h"
+
+#include <string.h>
+
+#if defined(_MSC_VER)
+#define VICTRONBLE_WEAK
+#else
+#define VICTRONBLE_WEAK __attribute__((weak))
+#endif
+
+VICTRONBLE_WEAK
+int victronble_aes_ctr_default(const uint8_t key[16], const uint8_t iv[16],
+                               const uint8_t *in, uint8_t *out,
+                               size_t len, void *user)
+{
+    (void)user;
+
+    struct vble_aes_ctx ctx;
+
+    vble_aes_init_ctx_iv(&ctx, key, iv);
+    if (out != in) {
+        memcpy(out, in, len);
+    }
+    vble_aes_ctr_xcrypt(&ctx, out, len);
+    return 0;
+}