feat: 친구 요청 보내기 컨트롤러 (#8)

controllers/friendController.js

+const FriendService = require('../services/friendService');
+
+class friendController {
+    /**
+     * 친구 요청 보내기
+     * POST /api/friend/request
+     */
+    async sendRequest(req, res) {
+        try {
+            const userId = req.user.id;
+            const { friendId } = req.body;
+
+            const request = await FriendService.sendFriendRequest(userId, friendId);
+            return res.status(201).json({
+                success: true,
+                data: request
+            });
+        } catch (error) {
+            return res.status(400).json({
+                success: false,
+                error: {
+                    message: error.message,
+                    code: 'FRIEND_REQUEST_ERROR'
+                }
+            });
+        }
+    }
+}
+
+module.exports = new friendController();
\ No newline at end of file