Settings → Capacity flags a crew concurrency set below its ceiling and resets it in one click #9049

Replaces #8960. Measured pacing shipped in 8a8980d9 (#9002). What's left is the live value: a crew.concurrency lowered at runtime still holds the crew back, and nothing shows it.

Done when:

• [x] Settings → Capacity marks any capacity key set below its default ceiling (the default from src/core/capacity.ts), showing the ceiling beside the value.
• [x] An admin can reset a key to its default with one same-origin POST, and the change is logged like other capacity changes.
• [x] The usage page's pace sentence says when concurrency is below its ceiling, so pacing is not mistaken for the cap.
• [x] Tests: a lowered value is flagged and the reset clears it; a value at the ceiling is not flagged; a cross-origin reset is refused.

Files: src/core/capacity.ts, the settings capacity page in src/web/, the usage page, test/.

Reviewed pull #9057 at its head: ticked Settings → Capacity marks any capacity key set below its default ceiling (the default from src/core/capacity.ts), showing the ceiling beside the value.; An admin can reset a key to its default with one same-origin POST, and the change is logged like other capacity changes.; The usage page's pace sentence says when concurrency is below its ceiling, so pacing is not mistaken for the cap.; Tests: a lowered value is flagged and the reset clears it; a value at the ceiling is not flagged; a cross-origin reset is refused..