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/postgres_store.go

@@ -157,6 +157,10 @@ func (p *Postgres) GetPostThread(ctx context.Context, rootID string) (*Post, err
 	return GetPostThread(ctx, p.db, rootID)
 }
 
+func (p *Postgres) GetPostThreadForViewer(ctx context.Context, rootID, viewerID string) (*Post, error) {
+	return GetPostThreadForViewer(ctx, p.db, rootID, viewerID)
+}
+
 func (p *Postgres) UpdatePost(ctx context.Context, post *Post) error {
 	post.db = p.db
 	return post.Update(ctx)
@@ -166,6 +170,18 @@ func (p *Postgres) ListRootPosts(ctx context.Context, postDate, viewerID string)
 	return ListRootPosts(ctx, p.db, postDate, viewerID)
 }
 
+func (p *Postgres) ListRootPostsByAuthor(ctx context.Context, authorID string) ([]Post, error) {
+	return ListRootPostsByAuthor(ctx, p.db, authorID)
+}
+
+func (p *Postgres) ListRootPostsAnsweredBy(ctx context.Context, adminID string) ([]Post, error) {
+	return ListRootPostsAnsweredBy(ctx, p.db, adminID)
+}
+
+func (p *Postgres) SetRootPostState(ctx context.Context, id string, state PostState) error {
+	return SetRootPostState(ctx, p.db, id, state)
+}
+
 func (p *Postgres) VotePost(ctx context.Context, userID, postID string, value int) error {
 	return SetPostVote(ctx, p.db, userID, postID, value)
 }