feat: reconcile SQLite tables and columns at startup

internal/database/workflow.go

@@ -466,27 +466,6 @@ func (db *DB) ListWorkflowRunsAwaitingHITLFiltered(conversationID string, limit
 	return out, rows.Err()
 }
 
-func (db *DB) migrateWorkflowRunsTable() error {
-	cols := []struct{ name, ddl string }{
-		{"pending_hitl_node_id", "ALTER TABLE workflow_runs ADD COLUMN pending_hitl_node_id TEXT"},
-		{"pending_hitl_json", "ALTER TABLE workflow_runs ADD COLUMN pending_hitl_json TEXT"},
-	}
-	for _, col := range cols {
-		var count int
-		err := db.QueryRow("SELECT COUNT(*) FROM pragma_table_info('workflow_runs') WHERE name=?", col.name).Scan(&count)
-		if err != nil || count > 0 {
-			continue
-		}
-		if _, err := db.Exec(col.ddl); err != nil {
-			errMsg := strings.ToLower(err.Error())
-			if !strings.Contains(errMsg, "duplicate column") && !strings.Contains(errMsg, "already exists") {
-				return err
-			}
-		}
-	}
-	return nil
-}
-
 func nullString(v string) interface{} {
 	v = strings.TrimSpace(v)
 	if v == "" {