Phase 7: MCP handler (25 tests), NIP-04 encrypt/decrypt (15 tests), CVM server skeleton

- mcp_handler.c/h: 4 tools (get_config, set_config, get_balance, wallet_send)
- nip04.c/h: AES-256-CBC + ECDH with 0x02 compressed pubkey prefix
  - Fixed IV copy bug: mbedTLS AES-CBC modifies IV in-place
  - Base64 encode/decode for ciphertext transport
  - PKCS7 padding
- cvm_server.c/h: Nostr DM listener with FreeRTOS task
- config: cvm_enabled, cvm_relays fields
- 156 total tests passing across 10 test binaries

1 files changed, 36 insertions, 0 deletions

diff --git a/main/mcp_handler.h b/main/mcp_handler.h
new file mode 100644
index 0000000..e42b5ee
--- /dev/null
+++ b/main/mcp_handler.h
@@ -0,0 +1,36 @@
+#ifndef MCP_HANDLER_H
+#define MCP_HANDLER_H
+
+#include <stdint.h>
+#include <stdbool.h>
+
+typedef enum {
+    MCP_TOOL_GET_CONFIG = 0,
+    MCP_TOOL_SET_CONFIG = 1,
+    MCP_TOOL_GET_BALANCE = 2,
+    MCP_TOOL_WALLET_SEND = 3,
+    MCP_TOOL_UNKNOWN = 99
+} mcp_tool_t;
+
+typedef struct {
+    mcp_tool_t tool;
+    char method[64];
+    char params_json[1024];
+} mcp_request_t;
+
+typedef struct {
+    bool success;
+    char result_json[2048];
+    char error[256];
+} mcp_response_t;
+
+mcp_tool_t mcp_parse_tool(const char *method);
+
+mcp_response_t mcp_handle_get_config(void);
+mcp_response_t mcp_handle_set_config(const char *params_json);
+mcp_response_t mcp_handle_get_balance(void);
+mcp_response_t mcp_handle_wallet_send(const char *params_json);
+
+mcp_response_t mcp_dispatch(const mcp_request_t *req);
+
+#endif