feat: add OpenAI markdown format endpoint

src/main/java/com/openisle/controller/AiController.java

@@ -0,0 +1,30 @@
+package com.openisle.controller;
+
+import com.openisle.service.OpenAiService;
+import lombok.RequiredArgsConstructor;
+import org.springframework.http.ResponseEntity;
+import org.springframework.web.bind.annotation.PostMapping;
+import org.springframework.web.bind.annotation.RequestBody;
+import org.springframework.web.bind.annotation.RequestMapping;
+import org.springframework.web.bind.annotation.RestController;
+
+import java.util.Map;
+
+@RestController
+@RequestMapping("/api/ai")
+@RequiredArgsConstructor
+public class AiController {
+
+    private final OpenAiService openAiService;
+
+    @PostMapping("/format")
+    public ResponseEntity<Map<String, String>> format(@RequestBody Map<String, String> req) {
+        String text = req.get("text");
+        if (text == null) {
+            return ResponseEntity.badRequest().build();
+        }
+        return openAiService.formatMarkdown(text)
+                .map(t -> ResponseEntity.ok(Map.of("content", t)))
+                .orElse(ResponseEntity.status(500).build());
+    }
+}