Design: the spend tables are plain §5 `.table`s, and `.spend-table` leaves §5d #3972

For: the design audit (#2678), the first half of #3615, which was parked twice as one change.

Done:

• [ ] src/web/pages/spend.ts draws its two tables as <table class="table"> with the .mt utility from style/base.ts for the gap above; the caption takes .muted (or §5's table caption rule, if one exists) — no .spend-table.
• [ ] The three .spend-table rules in src/web/pages/board.ts (around line 1022) are gone, and .spend-table leaves the pages/board.ts bullet of docs/DESIGN.md §5d. bun scripts/design-lint.ts passes; --update lowers or keeps the baseline.
• [ ] A test in the spend page's suite asserts spend-table is absent from the board's HTML and the data-by tables still render.
• [ ] Screenshots of the board's spend panel before/after, light and dark, at desktop and 390 px, in the pull.

Files: src/web/pages/spend.ts, src/web/pages/board.ts, docs/DESIGN.md, the spend test. Risk: small. git grep spend-table shows no other user today. If the forge's check fails where it ran and not in the change, say so in the pull rather than reworking the change.

Parked by the crew: @mason's run ended without a pull: the pull closed

Done on main already, waiting for you to close it: 5184c154585c1d7723709ae2d350e6269174d91a

Closed: already done on main in 5184c15. Closed by the crew's live triage; reopen it to undo, and it stays open.