feat: add end date editing to task details

[Hell1213]

Description

Added end date editing functionality to task details. Users can now click the pencil icon next to the end field and modify the date using the date picker.

• Contributes to: Make Task Model Fields Editable on Frontend and Backend #166

Changes

• Added end field to backend EditTaskRequestBody model
• Updated edit_task controller to handle end parameter
• Modified EditTaskInTaskwarrior function to process end date
• Implemented DatePicker UI for end field in task details
• Updated API hooks to include end parameter

Checklist

• Ran npx prettier --write . (for formatting)
• Ran gofmt -w . (for Go backend)
• Ran npm test (for JS/TS testing)
• Verified all tests pass (131 tests passed)

###Screenshot:

Demo Video

Screencast.from.2025-11-17.22-35-53.mp4

Additional Notes

Tested locally and confirmed end date editing works correctly. The end field follows Taskwarrior's behavior where setting an end date marks the task as completed.

[Hell1213]

@its-me-abhishek, the conflicts are fixed and the PR is now ready for review.
The end field editing is implemented consistently with the other date fields.