Address PR review: graceful shutdown, Role/NewUser, drop SQLite.

internal/store/migrate.go

@@ -3,24 +3,14 @@ package store
 import (
 	"database/sql"
 	"fmt"
-	"strings"
 )
 
-func migrateUserProfileColumns(db *sql.DB, dialect string) error {
+// migrateUserProfileColumns adds avatar_url and state when missing (existing DBs).
+func migrateUserProfileColumns(db *sql.DB) error {
 	cols := []string{"avatar_url", "state"}
 	for _, col := range cols {
-		var stmt string
-		switch dialect {
-		case dialectPostgres:
-			stmt = fmt.Sprintf(`ALTER TABLE users ADD COLUMN IF NOT EXISTS %s TEXT NOT NULL DEFAULT ''`, col)
-		default:
-			stmt = fmt.Sprintf(`ALTER TABLE users ADD COLUMN %s TEXT NOT NULL DEFAULT ''`, col)
-		}
+		stmt := fmt.Sprintf(`ALTER TABLE users ADD COLUMN IF NOT EXISTS %s TEXT NOT NULL DEFAULT ''`, col)
 		if _, err := db.Exec(stmt); err != nil {
-			// SQLite errors when the column already exists.
-			if dialect == dialectSQLite && strings.Contains(strings.ToLower(err.Error()), "duplicate column") {
-				continue
-			}
 			return fmt.Errorf("add column %s: %w", col, err)
 		}
 	}