[Chore] #218 - 개인정보 수정 닉네임 관련 로직 수정

Author: OneTen19

CERTI-iOS/Presentation/MyPage/View/EditProfileView.swift

@@ -146,14 +146,15 @@ extension EditProfileView {
             } label: {
                 Text("중복 확인")
                     .applyCertiFont(.caption_regular_12)
-                    .foregroundStyle(viewModel.nickNameValid == .valid ? .grayscale300 : .grayscale600)
+                    .foregroundStyle(viewModel.isNickNameChanged ? .grayscale600 : .grayscale300)
                     .padding(.vertical, 4)
                     .padding(.horizontal, 12)
                     .overlay {
                         Capsule()
-                            .stroke(viewModel.nickNameValid == .valid ? .grayscale200 : .grayscale300, lineWidth: 1)
+                            .stroke(viewModel.isNickNameChanged ? .grayscale300 : .grayscale200, lineWidth: 1)
                     }
             }
+            .disabled(!viewModel.isNickNameChanged)
         }
         .padding(.horizontal, 20)
         .padding(.bottom, 12)

CERTI-iOS/Presentation/MyPage/ViewModel/MyPageViewModel.swift

@@ -110,6 +110,11 @@ final class MyPageViewModel: ObservableObject {
         let profileImageURL: String
     }
 
+    var isNickNameChanged: Bool {
+        guard let initial = initialProfile else { return false }
+        return userNickName != initial.nickName && !userNickName.isEmpty
+    }
+    
     var isProfileModified: Bool {
         if selectedUIImage != nil { return true }