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>

db/queries/posts.sql

@@ -44,6 +44,16 @@ FROM thread
 JOIN users u ON u.id = thread.author_id
 ORDER BY thread.created_at, thread.id;
 
+-- name: GetRootPostVoteSummary :one
+SELECT
+  COALESCE(SUM(value), 0)::bigint AS score,
+  COALESCE(
+    MAX(value) FILTER (WHERE user_id = sqlc.arg(viewer_id)),
+    0
+  )::bigint AS user_vote
+FROM post_votes
+WHERE post_id = sqlc.arg(root_id);
+
 -- name: UpdatePost :execrows
 UPDATE posts
 SET
@@ -51,6 +61,14 @@ SET
   updated_at = sqlc.arg(updated_at)
 WHERE id = sqlc.arg(id);
 
+-- name: UpdateRootPostState :execrows
+UPDATE posts
+SET
+  post_state = sqlc.arg(post_state),
+  updated_at = sqlc.arg(updated_at)
+WHERE id = sqlc.arg(id)
+  AND parent_id IS NULL;
+
 -- name: ListRootPosts :many
 WITH RECURSIVE roots AS (
   SELECT p.*
@@ -100,6 +118,46 @@ LEFT JOIN post_votes viewer_vote
 ORDER BY score DESC, roots.created_at, roots.id
 LIMIT sqlc.arg(row_limit);
 
+-- name: ListRootPostsByAuthor :many
+SELECT
+  p.id, p.parent_id, p.author_id,
+  u.name AS author_name, u.role AS author_role,
+  p.title, p.body, p.city, p.post_date,
+  p.post_state, p.created_at, p.updated_at
+FROM posts p
+JOIN users u ON u.id = p.author_id
+WHERE p.parent_id IS NULL
+  AND p.author_id = sqlc.arg(author_id)
+  AND p.post_state <> sqlc.arg(hidden_state)
+ORDER BY p.created_at DESC, p.id DESC
+LIMIT sqlc.arg(row_limit);
+
+-- name: ListRootPostsAnsweredBy :many
+WITH RECURSIVE ancestors AS (
+  SELECT p.id, p.parent_id
+  FROM posts p
+  WHERE p.author_id = sqlc.arg(admin_id)
+    AND p.parent_id IS NOT NULL
+
+  UNION
+
+  SELECT parent.id, parent.parent_id
+  FROM posts parent
+  JOIN ancestors child ON child.parent_id = parent.id
+)
+SELECT DISTINCT
+  root.id, root.parent_id, root.author_id,
+  u.name AS author_name, u.role AS author_role,
+  root.title, root.body, root.city, root.post_date,
+  root.post_state, root.created_at, root.updated_at
+FROM posts root
+JOIN ancestors ON ancestors.id = root.id
+JOIN users u ON u.id = root.author_id
+WHERE root.parent_id IS NULL
+  AND root.post_state <> sqlc.arg(hidden_state)
+ORDER BY root.created_at DESC, root.id DESC
+LIMIT sqlc.arg(row_limit);
+
 -- name: PostIsVisibleRoot :one
 SELECT EXISTS(
   SELECT 1