Add missing blocked/gated/stopped status filter options to pipeline page#

Problem#

The pipeline page status filter dropdown was missing three valid status values: blocked, gated, and stopped. Users could not filter the pipeline view by these statuses.

Task / Link#

Closes #50

Changes#

• Added blocked, gated, and stopped <option> elements to the status filter <select> in app/pipeline/page.tsx
• Reordered options to: All statuses → Active → Blocked → Gated → Complete → Failed → Stuck → Paused → Stopped

Notes#

Option values match backend status strings exactly — no filtering logic changes required.

Testing#

• npm run lint passes with zero warnings
• npm run build compiles successfully