fix: resolve user registration error by fixing database queries

- Update CreateUser query to explicitly select only existing columns
- Update all user SELECT queries to explicitly select columns to avoid scan_frequency_minutes column issues
- Add GetUserForLogin query that includes password_hash for authentication
- Update login handler to use GetUserForLogin instead of GetUserByEmailOrUsername
- This prevents errors when migration hasn't been applied yet, allowing user registration to work

internal/database/queries/queries.sql

@@ -1,16 +1,19 @@
 -- name: CreateUser :one
 INSERT INTO users (email, username, password_hash, theme)
 VALUES ($1, $2, $3, $4)
-RETURNING *;
+RETURNING id, email, username, theme, created_at, updated_at;
 
 -- name: GetUserByEmail :one
-SELECT * FROM users WHERE email = $1;
+SELECT id, email, username, theme, created_at, updated_at FROM users WHERE email = $1;
 
 -- name: GetUserByUsername :one
-SELECT * FROM users WHERE username = $1;
+SELECT id, email, username, theme, created_at, updated_at FROM users WHERE username = $1;
 
 -- name: GetUserByEmailOrUsername :one
-SELECT * FROM users WHERE email = $1 OR username = $1;
+SELECT id, email, username, theme, created_at, updated_at FROM users WHERE email = $1 OR username = $1;
+
+-- name: GetUserForLogin :one
+SELECT id, email, username, password_hash, theme, created_at, updated_at 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;