The flow panel on /boards says the idle pulls and the parked count, each linking to what it names #6480

This makes the idle-pull and parked reads reachable on the page.

Done:

• [ ] src/web/pages/flow-panel.ts draws two lines under the existing flow numbers. The first is N idle pulls, linking the oldest three by number (from src/flow/idle_pulls.ts). The second is N parked today, M this week, linking the newest parked issue (from src/flow/parked.ts). A line whose number is 0 is not drawn.
• [ ] Signed out, both lines read with publicOnly.
• [ ] test/flow-panel-idle-parked.test.ts seeds one idle pull and one parked issue and finds both lines and their links. With neither, it finds no line.
• [ ] bun scripts/design-lint.ts passes. The lines reuse the panel's existing classes.

Files: src/web/pages/flow-panel.ts, test/flow-panel-idle-parked.test.ts