Fix/dropdown in add new task

[vijay-talsangi]

Description

Fix project dropdown displaying blank when creating a new project in Add Task dialog.

Problem: When selecting "+ Create new project…" from the Project dropdown while adding a task, the dropdown would show "Select a project" initially and then become blank while typing the new project name. This was confusing for users.

Solution:

Updated the Select component's value to use CREATE_NEW when isCreatingNewProject is true
Added dynamic text display in SelectValue that shows:
"+ Create new project…" when the option is first selected
"New: [project name]" as the user types the new project name
This provides clear visual feedback about the active selection state.

• Fixes: Project dropdown does not display selected value when creating a new project #259

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

File changed:
frontend/src/components/HomeComponents/Tasks/AddTaskDialog.tsx

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