refactor: null 처리 개선 및 경고 해결

### 주요 변경사항

#### null 처리 개선
- Repository 패턴: Get 메서드는 null 반환, Update/Delete는 예외 발생
- Service 레벨: Repository null 반환 시 적절한 예외 처리
- 명확한 책임 분리: Repository(데이터 접근) vs Service(비즈니스 로직)

#### 경고 해결 (20개 → 0개)
- null 참조 관련 경고 해결
- async 메서드 최적화 (Task.CompletedTask 사용)
- 타입 불일치 해결 (Dictionary, nullable 타입)
- 반환 타입 일치 (CharacterDto? → CharacterDto)

#### 코드 정리
- ProjectVG.Application.csproj에서 존재하지 않는 LLM 폴더 제거 항목 삭제
- DesignTimeDbContextFactory에서 Console.WriteLine 제거
- InMemory Repository 파일들 삭제 (SqlServer Repository만 사용)

#### Repository 패턴 개선
- 일관된 예외 처리: NotFoundException 사용
- Update 메서드: 무조건 반환하도록 수정
- Delete 메서드: 존재하지 않는 경우 예외 발생

Author: ImGdevel

ProjectVG.Application/Models/User/UserDto.cs

@@ -8,8 +8,8 @@ public class UserDto
         public string Username { get; set; } = string.Empty;
         public string Name { get; set; } = string.Empty;
         public string Email { get; set; } = string.Empty;
-        public string? ProviderId { get; set; }
-        public string? Provider { get; set; }
+        public string ProviderId { get; set; } = string.Empty;
+        public string Provider { get; set; } = string.Empty;
         public bool IsActive { get; set; }
         public DateTime CreatedAt { get; set; }
         public DateTime UpdatedAt { get; set; }

ProjectVG.Application/ProjectVG.Application.csproj

@@ -6,12 +6,6 @@
     <ImplicitUsings>enable</ImplicitUsings>
   </PropertyGroup>
 
-  <ItemGroup>
-    <Compile Remove="Services\LLM\**" />
-    <EmbeddedResource Remove="Services\LLM\**" />
-    <None Remove="Services\LLM\**" />
-  </ItemGroup>
-
   <ItemGroup>
     <PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="8.0.0" />
     <PackageReference Include="Microsoft.Extensions.Logging.Abstractions" Version="8.0.0" />

ProjectVG.Application/Services/Character/CharacterService.cs

@@ -1,6 +1,8 @@
 using ProjectVG.Infrastructure.Persistence.Repositories.Characters;
 using Microsoft.Extensions.Logging;
 using ProjectVG.Application.Models.Character;
+using ProjectVG.Common.Exceptions;
+using ProjectVG.Common.Constants;
 
 namespace ProjectVG.Application.Services.Character
 {
@@ -23,11 +25,11 @@ public async Task<IEnumerable<CharacterDto>> GetAllCharactersAsync()
             return characterDtos;
         }
 
-        public async Task<CharacterDto> GetCharacterByIdAsync(Guid id)
+        public async Task<CharacterDto?> GetCharacterByIdAsync(Guid id)
         {
             var character = await _characterRepository.GetByIdAsync(id);
             if (character == null) {
-                throw new NotFoundException(ErrorCode.CHARACTER_NOT_FOUND, id);
+                return null;
             }
 
             var characterDto = new CharacterDto(character);

ProjectVG.Application/Services/Chat/Factories/ChatLLMFormat.cs

@@ -89,7 +89,7 @@ [neutral] 내가 그런다고 좋아할 것 같아? [shy] 하지만 츄 해준
 ";
         }
 
-        private ChatOutputFormatResult ParseChatResponse(string llmText, string voiceName = null)
+        private ChatOutputFormatResult ParseChatResponse(string llmText, string? voiceName = null)
         {
             if (string.IsNullOrWhiteSpace(llmText))
                 return new ChatOutputFormatResult();
@@ -102,7 +102,7 @@ private ChatOutputFormatResult ParseChatResponse(string llmText, string voiceNam
             var matches = Regex.Matches(response, @"\[(.*?)\]\s*([^\[]+)");
 
             // 보이스별 감정 매핑
-            Dictionary<string, string> emotionMap = null;
+            Dictionary<string, string>? emotionMap = null;
             if (!string.IsNullOrWhiteSpace(voiceName))
             {
                 var profile = VoiceCatalog.GetProfile(voiceName);

ProjectVG.Application/Services/Chat/Factories/UserInputAnalysisLLMFormat.cs

@@ -155,7 +155,7 @@ private UserInputAnalysis ParseChatAction(Dictionary<string, string> response)
         {
             var conversationContext = response.GetValueOrDefault("CONTEXT", "일반적인 대화");
             var userIntent = response.GetValueOrDefault("INTENT", "대화");
-            var enhancedQuery = response.GetValueOrDefault("ENHANCED_QUERY", null);
+            var enhancedQuery = response.GetValueOrDefault("ENHANCED_QUERY", "");
 
             // 키워드 파싱
             var keywords = ParseKeywords(response.GetValueOrDefault("KEYWORDS", ""));

ProjectVG.Application/Services/User/UserService.cs

@@ -1,5 +1,7 @@
 using ProjectVG.Infrastructure.Persistence.Repositories.Users;
 using ProjectVG.Application.Models.User;
+using ProjectVG.Common.Exceptions;
+using ProjectVG.Common.Constants;
 
 namespace ProjectVG.Application.Services.User
 {

ProjectVG.Application/Services/WebSocket/WebSocketManager.cs

@@ -49,7 +49,7 @@ public async Task SendAsync(string sessionId, WebSocketMessage message)
 
         public async Task SendTextAsync(string sessionId, string text)
         {
-            if (_connectionRegistry.TryGet(sessionId, out var connection)) {
+            if (_connectionRegistry.TryGet(sessionId, out var connection) && connection != null) {
                 await connection.SendTextAsync(text);
                 _logger.LogDebug("WebSocket 텍스트 전송: {SessionId}", sessionId);
             }
@@ -60,7 +60,7 @@ public async Task SendTextAsync(string sessionId, string text)
 
         public async Task SendBinaryAsync(string sessionId, byte[] data)
         {
-            if (_connectionRegistry.TryGet(sessionId, out var connection)) {
+            if (_connectionRegistry.TryGet(sessionId, out var connection) && connection != null) {
                 await connection.SendBinaryAsync(data);
                 _logger.LogDebug("WebSocket 바이너리 전송: {SessionId}, {Length} bytes", sessionId, data?.Length ?? 0);
             }
@@ -69,10 +69,11 @@ public async Task SendBinaryAsync(string sessionId, byte[] data)
             }
         }
 
-        public async Task DisconnectAsync(string sessionId)
+        public Task DisconnectAsync(string sessionId)
         {
             _connectionRegistry.Unregister(sessionId);
             _logger.LogInformation("WebSocket 세션 해제: {SessionId}", sessionId);
+            return Task.CompletedTask;
         }
 
         public bool IsSessionActive(string sessionId)
@@ -101,12 +102,13 @@ public async Task HandleMessageAsync(string sessionId, string message)
             }
         }
 
-        public async Task HandleBinaryMessageAsync(string sessionId, byte[] data)
+        public Task HandleBinaryMessageAsync(string sessionId, byte[] data)
         {
             _logger.LogDebug("WebSocket 바이너리 메시지 처리: {SessionId}, {Length} bytes", sessionId, data?.Length ?? 0);
 
             // 바이너리 메시지 처리 로직 구현
             // 예: 오디오 데이터, 파일 업로드 등
+            return Task.CompletedTask;
         }
 
         private async Task ProcessMessageAsync(string sessionId, WebSocketMessage message)
@@ -130,11 +132,12 @@ private async Task HandlePingAsync(string sessionId)
             await SendAsync(sessionId, pongMessage);
         }
 
-        private async Task HandleChatMessageAsync(string sessionId, WebSocketMessage message)
+        private Task HandleChatMessageAsync(string sessionId, WebSocketMessage message)
         {
             // 채팅 메시지 처리 로직
             // ChatService와 연동하여 처리
             _logger.LogInformation("채팅 메시지 수신: {SessionId}", sessionId);
+            return Task.CompletedTask;
         }
 
         private string GenerateSessionId()

ProjectVG.Infrastructure/GlobalUsings.cs

@@ -0,0 +1,4 @@
+global using Microsoft.Extensions.Logging;
+
+global using ProjectVG.Common.Constants;
+global using ProjectVG.Common.Exceptions;

ProjectVG.Infrastructure/Integrations/MemoryClient/VectorMemoryClient.cs

@@ -68,9 +68,12 @@ public async Task<List<MemorySearchResult>> SearchAsync(string collection, strin
                     PropertyNameCaseInsensitive = true
                 });
 
-                _logger.LogInformation("[MemoryStore] Search 결과 {Count}개:", results.Count);
-                foreach (var result in results) {
-                    _logger.LogInformation(" - Text: {Text}, Score: {Score:F4}", result.Text, result.Score);
+                _logger.LogInformation("[MemoryStore] Search 결과 {Count}개:", results?.Count ?? 0);
+                if (results != null)
+                {
+                    foreach (var result in results) {
+                        _logger.LogInformation(" - Text: {Text}, Score: {Score:F4}", result.Text, result.Score);
+                    }
                 }
 
                 return results ?? new List<MemorySearchResult>();

ProjectVG.Infrastructure/Integrations/TextToSpeechClient/Models/TextToSpeechRequest.cs

@@ -5,7 +5,7 @@ namespace ProjectVG.Infrastructure.Integrations.TextToSpeechClient.Models
     public class TextToSpeechRequest
     {
         [JsonIgnore]
-        public string VoiceId { get; set; }
+        public string VoiceId { get; set; } = string.Empty;
 
         /// <summary>
         /// 텍스트를 음성으로 변환할 내용 (최대 300자)