Sprint 6F: approval execution and execution review UI

[samrusani]

Summary

• extend the existing approvals and tasks UI to execute eligible approved requests through the shipped backend seam
• surface resulting execution state in bounded approval and task review panels with explicit loading, success, failure, and unavailable states
• keep the sprint inside the existing approval-execution and execution-review backend contract with no broader workflow expansion

Verification

• npm run lint in apps/web: PASS
• npm test in apps/web: PASS (4 files, 20 tests)
• npm run build in apps/web: PASS

Notes

• the sprint stayed a UI sprint and used only the shipped approval-execution and execution-review seams
• no backend, Gmail, Calendar, auth, runner, or broader workflow expansion entered the diff