Add nested posts UI (#5)

## Summary
- Cut hunt, question, submission, voting, hiding, and profile flows over to unified posts
- Render nested replies with permission-aware inline Reply/Edit controls and edited markers
- Add post profile queries and the author index migration they depend on

Co-authored-by: codegirl-007 <s.raide@gmail.com>

internal/store/memory.go

@@ -438,6 +438,21 @@ func (m *Memory) GetPostThread(_ context.Context, rootID string) (*Post, error)
 	return buildPostTree(posts, rootID)
 }
 
+func (m *Memory) GetPostThreadForViewer(ctx context.Context, rootID, viewerID string) (*Post, error) {
+	root, err := m.GetPostThread(ctx, rootID)
+	if err != nil {
+		return nil, err
+	}
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	for _, value := range m.postVotes[rootID] {
+		root.Score += value
+	}
+	root.UserVote = m.postVotes[rootID][viewerID]
+	root.Answered = m.threadContainsAdminReply(rootID)
+	return root, nil
+}
+
 func (m *Memory) UpdatePost(_ context.Context, post *Post) error {
 	if post == nil {
 		return fmt.Errorf("%w: post is nil", ErrInvalidPost)
@@ -489,6 +504,73 @@ func (m *Memory) ListRootPosts(_ context.Context, postDate, viewerID string) ([]
 	return posts, nil
 }
 
+func (m *Memory) ListRootPostsByAuthor(_ context.Context, authorID string) ([]Post, error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	posts := make([]Post, 0)
+	for _, post := range m.posts {
+		if post.ParentID != nil ||
+			post.AuthorID != authorID ||
+			post.PostState == PostStateHidden {
+			continue
+		}
+		posts = append(posts, *clonePostWithAuthor(post, m.users))
+	}
+	return sortProfilePosts(posts), nil
+}
+
+func (m *Memory) ListRootPostsAnsweredBy(_ context.Context, adminID string) ([]Post, error) {
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	posts := make([]Post, 0)
+	for _, root := range m.posts {
+		if root.ParentID != nil || root.PostState == PostStateHidden {
+			continue
+		}
+		participated := false
+		for _, post := range m.posts {
+			if post.AuthorID == adminID && m.postIsDescendantOf(post, root.ID) {
+				participated = true
+				break
+			}
+		}
+		if participated {
+			posts = append(posts, *clonePostWithAuthor(root, m.users))
+		}
+	}
+	return sortProfilePosts(posts), nil
+}
+
+func (m *Memory) SetRootPostState(_ context.Context, id string, state PostState) error {
+	switch state {
+	case PostStateVisible, PostStateHidden, PostStateLocked:
+	default:
+		return fmt.Errorf("%w: invalid post state", ErrInvalidPost)
+	}
+	m.mu.Lock()
+	defer m.mu.Unlock()
+	post, ok := m.posts[id]
+	if !ok || post.ParentID != nil {
+		return sql.ErrNoRows
+	}
+	post.PostState = state
+	post.UpdatedAt = time.Now().UTC().Format(time.RFC3339Nano)
+	return nil
+}
+
+func sortProfilePosts(posts []Post) []Post {
+	sort.Slice(posts, func(i, j int) bool {
+		if posts[i].CreatedAt != posts[j].CreatedAt {
+			return posts[i].CreatedAt > posts[j].CreatedAt
+		}
+		return posts[i].ID > posts[j].ID
+	})
+	if len(posts) > ProfileListLimit {
+		posts = posts[:ProfileListLimit]
+	}
+	return posts
+}
+
 func (m *Memory) VotePost(_ context.Context, userID, postID string, value int) error {
 	m.mu.Lock()
 	defer m.mu.Unlock()