feat: add a theme picker (#11140)

coderd/database/queries/users.sql

@@ -80,7 +80,18 @@ SET
 	avatar_url = $4,
 	updated_at = $5
 WHERE
-	id = $1 RETURNING *;
+	id = $1
+RETURNING *;
+
+-- name: UpdateUserAppearanceSettings :one
+UPDATE
+	users
+SET
+	theme_preference = $2,
+	updated_at = $3
+WHERE
+	id = $1
+RETURNING *;
 
 -- name: UpdateUserRoles :one
 UPDATE
@@ -266,4 +277,3 @@ RETURNING id, email, last_seen_at;
 -- AllUserIDs returns all UserIDs regardless of user status or deletion.
 -- name: AllUserIDs :many
 SELECT DISTINCT id FROM USERS;
-