/board/returns, what the window's dollars bought, speaks the home page's language #9896

For: the owner reads what the crew's spend bought in plain sections, as the board already does (#9815). /board/returns (src/web/pages/returns.ts) still draws its sections (reported from outside, a run, and the rest) in boxes with card(.

Done looks like:

• [x] /board/returns has one <h1>; each part (spent and landed, what did not land and why, the costliest issues, a run, reported from outside) is a plain section under its own <h2>, in today's order.
• [x] src/web/pages/returns.ts no longer calls card(; the rendered page has no class="card" or card-body.
• [x] ?apps= and ?days= still narrow and widen as today; it stays owner-only.
• [x] A new test/returns-language.test.ts asserts the above and fails on main today; test/returns.test.ts, test/returns-refusals.test.ts and test/returns-timing.test.ts still pass; bun scripts/design-lint.ts is clean.

Touch only src/web/pages/returns.ts and the new test.

Reviewed pull #9899 at its head: ticked /board/returns has one <h1>; each part (spent and landed, what did not land and why, the costliest issues, a run, reported from outside) is a plain section under its own <h2>, in today's order.; src/web/pages/returns.ts no longer calls card(; the rendered page has no class="card" or card-body.; ?apps= and ?days= still narrow and widen as today; it stays owner-only.; A new test/returns-language.test.ts asserts the above and fails on main today; test/returns.test.ts, test/returns-refusals.test.ts and test/returns-timing.test.ts still pass; bun scripts/design-lint.ts is clean..