fix(security): apply valid range limits to api pagination input

[Shreyassp002]

Category: Security
Priority: P1
What: Safely parsed limit and offset query parameters in /api/v1/payment-links and /api/v1/transactions routes using isNaN checks and constraining to valid boundaries.
Why: The previous implementation allowed NaN and negative limits by incorrectly passing unvalidated strings into parseInt, causing invalid limit and offset values passed to Supabase's .range() query which could result in server errors or unconstrained data pulls.
Impact: Safe and predictable database queries, mitigating potential DoS or error spew.
Verification: Ran npm run lint and npm run build locally successfully.

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PR created automatically by Jules for task 4395534982611346774 started by @Shreyassp002

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Project	Deployment	Actions	Updated (UTC)
flash-protocol	Error		May 6, 2026 6:17am

[github-actions]

⚡ Flash Review

Metric	Value
Files Reviewed	2
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.