feat: add link modify api

Author: ytnwjd

src/main/java/com/ajouchong/controller/admin/LinkAdminController.java

@@ -31,6 +31,14 @@ public ApiResponse<List<LinkResponseDto>> getAllLinks() {
         return new ApiResponse<>(1, "링크 목록을 조회했습니다.", links);
     }
 
+    @PutMapping("/{id}")
+    public ApiResponse<LinkResponseDto> updateLink(@PathVariable Long id, 
+                                                   @Valid @RequestBody LinkRequestDto requestDto) {
+        LinkResponseDto response = linkService.updateLink(id, requestDto);
+        
+        return new ApiResponse<>(1, "링크가 성공적으로 수정되었습니다.", response);
+    }
+    
     @DeleteMapping("/{id}/delete")
     public ApiResponse<Void> deleteLink(@PathVariable Long id) {
         linkService.deleteLink(id);

src/main/java/com/ajouchong/controller/user/LinkController.java

@@ -1,13 +1,11 @@
 package com.ajouchong.controller.user;
 
 import com.ajouchong.common.ApiResponse;
-import com.ajouchong.dto.request.LinkRequestDto;
 import com.ajouchong.dto.response.LinkResponseDto;
 import com.ajouchong.service.LinkService;
 import lombok.RequiredArgsConstructor;
 import org.springframework.web.bind.annotation.*;
 
-import jakarta.validation.Valid;
 import java.util.List;
 
 @RestController
@@ -16,13 +14,6 @@
 public class LinkController {
     private final LinkService linkService;
 
-    @PostMapping("/upload")
-    public ApiResponse<LinkResponseDto> uploadLink(@Valid @RequestBody LinkRequestDto requestDto) {
-        LinkResponseDto response = linkService.uploadLink(requestDto);
-        
-        return new ApiResponse<>(1, "링크가 성공적으로 업로드되었습니다.", response);
-    }
-    
     @GetMapping
     public ApiResponse<List<LinkResponseDto>> getAllLinks() {
         List<LinkResponseDto> links = linkService.getAllLinks();

src/main/java/com/ajouchong/service/LinkService.java

@@ -55,6 +55,24 @@ public List<LinkResponseDto> getAllLinks() {
                 .collect(Collectors.toList());
     }
 
+    @Transactional
+    public LinkResponseDto updateLink(Long id, LinkRequestDto requestDto) {
+        Link link = linkRepository.findById(id)
+                .orElseThrow(() -> new IllegalArgumentException("링크를 찾을 수 없습니다. ID: " + id));
+        
+        link.setTitle(requestDto.getTitle());
+        link.setLink(requestDto.getLink());
+        
+        Link updatedLink = linkRepository.save(link);
+        
+        return LinkResponseDto.builder()
+                .id(updatedLink.getId())
+                .title(updatedLink.getTitle())
+                .link(updatedLink.getLink())
+                .createdAt(updatedLink.getCreatedAt())
+                .build();
+    }
+    
     @Transactional
     public void deleteLink(Long id) {
         Link link = linkRepository.findById(id)