Fix pipeline page repo and directive filters#

Problem#

The repo and directive text inputs on /pipeline used window.location.href for navigation, causing full page reloads that broke client-side state. On Enter, both onKeyDown and onBlur fired, triggering double navigation.

Task / Link#

Closes #51

Changes#

• Import useRouter from next/navigation and replace all window.location.href assignments with router.push()
• Add enterPressedRef to prevent onBlur from double-navigating after Enter is pressed on text inputs
• Update empty state message to "No tasks match the current filters" when any filter is active

Notes#

• Status dropdown and showE2e checkbox also migrated to router.push() for consistency
• Pagination prev/next migrated as well

Testing#

• Build passes (npm run build)
• Lint passes (npm run lint)