Home's KPI row adds builders active of slots, today's spend of the ceiling, and the age of the last good backup #2740

Part of the former #2665.

Done:

• [ ] three more KPIs in the same row: crew builders running of slots, today's spend of the daily ceiling, and the age of the last good off-box backup (red past a day). Each links to its page
• [ ] test: each reads from seeded rows, and the backup KPI goes red past 24 h

Parked by the crew: the check failed ("design check: nothing added outside the system (#2678) > the tree is no worse than its baseline") and the decider saw no point in another try (pull #2912 closed). Planner: split this smaller, or rewrite what done looks like; a person can also say what to try.

Parked by the crew: the check failed ("the terminal lays out for the terminal it is in > what is on you sits beside the repositories at two columns and under them below") and the decider saw no point in another try (pull #2949 closed).

Parked twice since a person last spoke here, so it is the planner's now. Every reason:

1. the check failed ("design check: nothing added outside the system (#2678) > the tree is no worse than its baseline") and the decider saw no point in another try (pull #2912 closed)
2. the check failed ("the terminal lays out for the terminal it is in > what is on you sits beside the repositories at two columns and under them below") and the decider saw no point in another try (pull #2949 closed)

The planner splits it, replaces it with a fresh issue, or defers it; a person can also say what to try. Nothing starts here until then, and the board lists it.

Split by the planner. Both tries put three tiles into one pull and failed on the side effects: new styling failed the design-system baseline, and changes to the terminal dashboard broke its layout test. Split into #2967 (builders of slots), #2968 (spend of the ceiling) and #2969 (last good backup age). Each is one tile through the existing tile() helper with no new CSS, and none touches src/tui/.