feat: add user preferences dashboard

- Add /preferences route and preferences.html template for user settings
- Implement username, email, password, and theme update functionality
- Add account deletion feature with confirmation
- Add navigation link to preferences from dashboard
- Create API endpoints:
  - PUT /api/user/username - Update username
  - PUT /api/user/email - Update email address
  - PUT /api/user/password - Change password with verification
  - DELETE /api/user/account - Delete user account
- Add database queries for user updates and account deletion
- Create Bruno API testing files for all user preference endpoints
- Add proper validation, error handling, and security checks

internal/database/queries/queries.sql

@@ -15,6 +15,9 @@ SELECT * FROM users WHERE email = $1 OR username = $1;
 -- name: GetUser :one
 SELECT id, email, username, theme, created_at, updated_at FROM users WHERE id = $1;
 
+-- name: GetUserPasswordHash :one
+SELECT password_hash FROM users WHERE id = $1;
+
 -- name: ListUsers :many
 SELECT id, email, username, theme, created_at, updated_at FROM users ORDER BY created_at DESC;
 
@@ -69,6 +72,18 @@ DELETE FROM reading_progress WHERE ebook_id = $1 AND user_id = $2;
 -- name: UpdateUserTheme :exec
 UPDATE users SET theme = $2, updated_at = NOW() WHERE id = $1;
 
+-- name: UpdateUsername :exec
+UPDATE users SET username = $2, updated_at = NOW() WHERE id = $1;
+
+-- name: UpdateEmail :exec
+UPDATE users SET email = $2, updated_at = NOW() WHERE id = $1;
+
+-- name: UpdatePassword :exec
+UPDATE users SET password_hash = $2, updated_at = NOW() WHERE id = $1;
+
+-- name: DeleteUser :exec
+DELETE FROM users WHERE id = $1;
+
 -- name: CreateEbookRating :one
 INSERT INTO ebook_ratings (ebook_id, user_id, rating)
 VALUES ($1, $2, $3)