fix: delete all tasks dialog state conflict

[Hell1213]

Description
Fixed delete all tasks dialog closing immediately and freezing screen by restoring proper DialogTrigger pattern with onSelect={(e) => e.preventDefault()} to match other dialogs in NavbarDesktop component.

Fixes: #321

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
Dialog now works correctly without screen freeze. Solution follows existing code patterns used by Export and DevLogs dialogs in the same component.

Demo

Screencast.from.2025-12-27.21-03-44.mp4

[github-actions]

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[Hell1213]

Restored proper DialogTrigger pattern with onSelect={(e) => e.preventDefault()}