remove exposed .h crypto headers

tests/chacha20_test.c

@@ -9,7 +9,15 @@
 #include <string.h>
 #include <stdlib.h>
 #include <stdint.h>
-#include "../nostr_core/crypto/nostr_chacha20.h"
+
+// Forward declarations for ChaCha20 functions (private API)
+// These functions are implemented in crypto/ but not exposed through public headers
+void chacha20_quarter_round(uint32_t state[16], int a, int b, int c, int d);
+int chacha20_block(const uint8_t key[32], uint32_t counter,
+                   const uint8_t nonce[12], uint8_t output[64]);
+int chacha20_encrypt(const uint8_t key[32], uint32_t counter,
+                     const uint8_t nonce[12], const uint8_t* input,
+                     uint8_t* output, size_t length);
 
 // Helper function to convert hex string to bytes
 static int hex_to_bytes(const char* hex, uint8_t* bytes, size_t len) {