[Developer] add Codex streamable MCP endpoint

src/main/java/com/cloudhandson/vpdbackoffice/web/McpSseController.java

@@ -29,6 +29,20 @@ public class McpSseController {
     this.mcpSseService = mcpSseService;
   }
 
+  /**
+   * Streamable HTTP transport for Codex and other current MCP clients.
+   * The legacy SSE endpoints remain available for existing integrations.
+   */
+  @PostMapping(path = "/mcp", consumes = MediaType.APPLICATION_JSON_VALUE, produces = MediaType.APPLICATION_JSON_VALUE)
+  public ResponseEntity<ObjectNode> streamableMessage(@RequestBody JsonNode request) {
+    // JSON-RPC notifications never receive a response body.  Current MCP
+    // clients send notifications/initialized immediately after initialize.
+    if (request != null && !request.has("id")) {
+      return ResponseEntity.accepted().build();
+    }
+    return ResponseEntity.ok(mcpSseService.handle("default", request));
+  }
+
   @GetMapping(path = "/mcp/sse", produces = MediaType.TEXT_EVENT_STREAM_VALUE)
   public SseEmitter defaultSse() throws IOException {
     return openSse("default");