refactor: Integrate user auth for post interactions and enable post creation

This commit enhances the post detail and creation flows by integrating user authentication and activating the post creation functionality.

**Key Changes:**

*   **refactor(PostDetailViewModel):**
    *   The `loadPostDetail` function no longer requires `userId` as a parameter. It now retrieves the current user's ID directly from the JWT using `TokenManager`.
    *   When creating a new comment (`CreateCommentDto`), the current `commentDateTime` (using `java.util.Date`) is now included.

*   **feat(PostViewModel):**
    *   The previously stubbed `createPost` function has been fully implemented.
    *   It now makes sequential repository calls: first to `createPostMetadata` to get a new `postId`, and then to `createPostBody` with that ID.
    *   The UI state is updated to reflect success or failure throughout the creation process.

app/src/main/java/com/qingshuige/tangyuan/viewmodel/PostDetailViewModel.kt

@@ -7,6 +7,7 @@ import com.qingshuige.tangyuan.model.CommentCard
 import com.qingshuige.tangyuan.model.CreateCommentDto
 import com.qingshuige.tangyuan.model.PostCard
 import com.qingshuige.tangyuan.model.PostDetailState
+import com.qingshuige.tangyuan.network.TokenManager
 import com.qingshuige.tangyuan.repository.PostDetailRepository
 import com.qingshuige.tangyuan.utils.ImageSaveUtils
 import dagger.hilt.android.lifecycle.HiltViewModel
@@ -16,6 +17,7 @@ import kotlinx.coroutines.flow.StateFlow
 import kotlinx.coroutines.flow.asStateFlow
 import kotlinx.coroutines.flow.catch
 import kotlinx.coroutines.launch
+import java.util.Date
 import javax.inject.Inject
 
 @HiltViewModel
@@ -24,6 +26,8 @@ class PostDetailViewModel @Inject constructor(
     @ApplicationContext private val context: Context
 ) : ViewModel() {
     
+    private val tokenManager = TokenManager()
+    
     private val _state = MutableStateFlow(PostDetailState())
     val state: StateFlow<PostDetailState> = _state.asStateFlow()
     
@@ -33,9 +37,9 @@ class PostDetailViewModel @Inject constructor(
     /**
      * 加载帖子详情和评论 - 分离加载，先加载帖子再加载评论
      */
-    fun loadPostDetail(postId: Int, userId: Int = 0) {
+    fun loadPostDetail(postId: Int) {
         currentPostId = postId
-        currentUserId = userId
+        currentUserId = tokenManager.getUserIdFromToken() ?: 0
         
         viewModelScope.launch {
             _state.value = _state.value.copy(isLoading = true, error = null)
@@ -57,7 +61,7 @@ class PostDetailViewModel @Inject constructor(
                         )
                         
                         // 然后异步加载评论
-                        loadComments(postId, userId)
+                        loadComments(postId, currentUserId)
                     }
             } catch (e: Exception) {
                 _state.value = _state.value.copy(
@@ -133,6 +137,7 @@ class PostDetailViewModel @Inject constructor(
             
             val createCommentDto = CreateCommentDto(
                 postId = currentPostId.toLong(),
+                commentDateTime = Date(),
                 content = content,
                 parentCommentId = if (parentCommentId == 0) null else parentCommentId.toLong(),
                 userId = currentUserId.toLong()

app/src/main/java/com/qingshuige/tangyuan/viewmodel/PostViewModel.kt

@@ -161,13 +161,26 @@ class PostViewModel @Inject constructor(
         viewModelScope.launch {
             _postUiState.value = _postUiState.value.copy(isCreating = true, error = null)
             try {
-                // TODO: Call repository createPost method
+                var postId: Int? = null
-                // val postId = postRepository.createPostMetadata(metadata)
+                
-                // postRepository.createPostBody(body.copy(postId = postId))
+                postRepository.createPostMetadata(metadata)
-                // _postUiState.value = _postUiState.value.copy(
+                    .catch { e -> throw e }
-                //     isCreating = false,
+                    .collect { id ->
-                //     createSuccess = true
+                        postId = id
-                // )
+                        
+                        postRepository.createPostBody(body.copy(postId = id))
+                            .catch { e -> throw e }
+                            .collect { success ->
+                                if (success) {
+                                    _postUiState.value = _postUiState.value.copy(
+                                        isCreating = false,
+                                        createSuccess = true
+                                    )
+                                } else {
+                                    throw Exception("Failed to create post body")
+                                }
+                            }
+                    }
             } catch (e: Exception) {
                 _postUiState.value = _postUiState.value.copy(
                     isCreating = false,