fix: validate and bound pagination limit and offset in API routes

[Shreyassp002]

Category: Bug
Priority: P1
What: Added isNaN and negative value checks to limit and offset parsing across four transaction and payment-link API routes. It ensures that variables use safe defaults and limits.
Why: If a client sends a non-numeric string (e.g. ?limit=abc), parseInt returns NaN, and Math.min(NaN, 100) evaluates to NaN. Passing NaN into Supabase database queries causes errors or undefined behaviors.
Impact: Prevents database query failures due to malformed pagination parameters.
Verification: Ran npm run lint and npm run build which passed successfully. Verified that package.json changes were omitted as per project boundaries.

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PR created automatically by Jules for task 13643944272714269455 started by @Shreyassp002

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Project	Deployment	Actions	Updated (UTC)
flash-protocol	Error		May 1, 2026 6:10am

[github-actions]

⚡ Flash Review

Metric	Value
Files Reviewed	4
Risk Level	🟢 Low
Issues Found	None

✅ This PR looks clean. No security issues, bugs, or significant improvements found.

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[Shreyassp002]

Closing as duplicate of #31 which has been merged.

[google-labs-jules]

Closing as duplicate of #31 which has been merged.

Understood. Acknowledging that this work is now obsolete and stopping work on this task.