fix: guard non-object target credentials.json in homedir migration

JSON.parse succeeds on null/string/number but `in` operator throws
TypeError on non-objects. Normalize parsed value to {} when not a
plain object.

[宪宪/Opus-46🐾]

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: mindfn

packages/api/src/config/catalog-accounts.ts

@@ -396,7 +396,10 @@ function migrateHomedirCredentials(projectRoot?: string): void {
     let targetCreds: Record<string, unknown> = {};
     if (existsSync(targetCredPath)) {
       try {
-        targetCreds = JSON.parse(readFileSync(targetCredPath, 'utf-8'));
+        const parsed = JSON.parse(readFileSync(targetCredPath, 'utf-8'));
+        if (typeof parsed === 'object' && parsed !== null && !Array.isArray(parsed)) {
+          targetCreds = parsed;
+        }
       } catch {
         targetCreds = {};
       }