Fix Date Validation in chunkDaysIntoWeeks Function

[tmdeveloper007]

Summary of What Has Been Done

Replaced the loose regex + new Date() validity check with explicit date component validation. The fix validates that month is 1-12 and uses a days-in-month lookup to reject impossible dates like "2024-02-30".

Changes Made

• lib/calculate.ts: Added explicit date component validation

Impact it Made

• Prevents garbage dates from polluting contribution calendar data
• Makes validation semantically correct

Closes #8844

Note: Please assign this PR to the tmdeveloper007 account.

[retenta-bot]

This PR enhances the date validation logic by replacing the previous loose regex and new Date() checks with explicit validation for date components. This change is crucial as it prevents garbage dates from polluting the contribution calendar data, aligning with our previous decisions on improving date validation. Thank you for your contribution!

[github-actions]

📦 Next.js Bundle Size Report (Gzipped Sizes)

✨ No significant bundle size changes detected.

📊 Summary of Totals

Category	PR Size	Base Size	Difference
Total JS	4939.27 KB	4939.27 KB	0 B
Total CSS	348.46 KB	348.46 KB	0 B

[Aamod007]

Excellent work on this date validation fix! Using explicit matching and checking the \daysInMonth\ ensures that impossible dates like 2024-02-30 are properly rejected, avoiding bad data from sneaking into the contribution calendar. The transition from a loose regex and generic
ew Date\ to strict validation in \lib/calculate.ts\ is exactly what's needed. Approved!