Build list filters: branch, status and job !100

Parity row "build list filters (ref, status, job)" (krz/gitbay 7de4e7b).

• BuildFilter renders --ref, --status and --job; a blank branch sends no flag.
• BuildListViewModel.filter reloads on change with the flags appended; the empty state says whether filters apply.
• A filter button on the builds screen opens a sheet with a branch field, a status menu (pending, running, success, failure, cancelled) and a job menu fed by build jobs, hidden when the repository has no CI config.