fix(tasks): resolve black screen when editing wait date field

[ShivaGupta-14]

Description

Replaced unsafe new Date() with safe date parsing in wait date DatePicker. Added error handling and validation to prevent RangeError crashes.

Fixes black screen bug caused by invalid date parsing.

• Fixes: Editing waitField results in a black screen #252

Checklist

• Ran npx prettier --write . (for formatting)
• Ran gofmt -w . (for Go backend)
• Ran npm test (for JS/TS testing)
• Added unit tests, if applicable
• Verified all tests pass
• Updated documentation, if needed

Additional Notes

Video

Screen.Recording.2025-12-07.at.8.54.53.PM.mov

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