🔒 Security Fix: Input Validation & Rate Limiting for Hint API

[APPLEPIE6969]

What:

• Implemented zod schema validation for the /api/quiz/hint endpoint.
• Added a rate limiter allowing 10 requests per minute per user/IP.
• Restored authentication checks (which were temporarily bypassed for testing).

Risk:

• Previously, the endpoint accepted arbitrarily large payloads, posing a Denial of Service (DoS) risk and potential cost abuse.
• Lack of rate limiting allowed unlimited automated requests.

Solution:

• Restricted question to max 1000 characters and context to max 500 characters.
• Invalid requests now return 400 Bad Request.
• Excessive requests now return 429 Too Many Requests.

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PR created automatically by Jules for task 12123468364466839176 started by @APPLEPIE6969

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Project	Deployment	Actions	Updated (UTC)
studyflow	Building	Preview, Comment	Feb 26, 2026 10:46pm