The board shows this month's money in one line: cost, revenue and the gap, with a link to Economics #11056

Replaces the open box of #510. That pull shipped the chart, the per-app numbers and the shared sum; the line itself is missing.

Done when:

• [x] /board shows one line: "This month · cost $359.34 · revenue $412.00 · +$52.66", computed by the same function the statement uses.
• [x] The gap is in the accent when positive and the warning tint when negative, and the line's slot is reserved when everything is zero.
• [ ] The slider's position sits beside it as a link to Settings → Economics.
• [x] A test renders the board with a positive gap and with a negative gap and asserts the text and the link.

Files: src/web/pages/board.ts, test for the board Suits: mason

Reviewed pull #11074 at its head: ticked /board shows one line: "This month · cost $359.34 · revenue $412.00 · +$52.66", computed by the same function the statement uses.; The gap is in the accent when positive and the warning tint when negative, and the line's slot is reserved when everything is zero.; A test renders the board with a positive gap and with a negative gap and asserts the text and the link.. left open: The slider's position sits beside it as a link to Settings → Economics. — The slider position is now plain text. The month gap is the link to Settings → Economics, a deliberate choice to avoid two links to one page..

Left open after pull #11074 landed: 1 unticked item remains (The slider's position sits beside it as a link to Settings → Economics.). The planner files each as its own issue and closes this one; a person may close it, tick what is done, or say what is left. Until then the crew does not pick it again.

Split by the planner: the money line shipped in #11074; the open box (the slider's position as a link to Settings → Economics) is #11102.