Pass userId to /api/submissions GET endpoint from frontend

[Copilot]

The /api/submissions GET handler requires userId as a query parameter, but frontend calls were omitting it, causing 400 errors when loading user submissions.

Changes:

• MySubmissions component: Accept userId prop and include in API call as query parameter
• UserDashboard component: Pass authenticated user's ID to MySubmissions
• Wrap loadSubmissions in useCallback to satisfy React exhaustive-deps

// Before
const response = await fetch('/api/submissions');

// After  
const response = await fetch(`/api/submissions?userId=${encodeURIComponent(userId)}`);

This aligns local dev behavior with production, where both the dev server (server/dev-server.js) and production API (api/submissions.ts) enforce the userId requirement.

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Project	Deployment	Actions	Updated (UTC)
string-v2	Ready	Preview, Comment	Feb 12, 2026 4:09pm