Account form errors draw the shared danger component, and the page-local .error-note class is gone #9081

Intent: one design system with no page-local classes; this replaces #7760, which waited on a dropped issue.

Today .error-note has its own rule in src/web/style/components.ts:144 and three uses in src/web/pages/account.ts (lines ~125, ~290, ~847), and is listed in docs/design/sections/5d-page-local-classes.md.

Done when:

• [ ] The three messages in src/web/pages/account.ts draw a component other forms already use for a refused submit, in the danger tone and with role="alert": the .toast[data-tone=danger] used in src/web/pages/browse.ts:1068, or the field .error (components.ts:131) where the message belongs to a field. No new class. The words are unchanged and still escaped.
• [ ] grep -rn error-note src docs finds nothing: the rule and the 5d entry are gone.
• [ ] A test posts a refused form on each of the three (notify URL, the form at ~290, the one at ~847), finds the message with role="alert", and finds no error-note. It fails on main.
• [ ] bun scripts/design-lint.ts passes.

Files: src/web/pages/account.ts, src/web/style/components.ts, docs/design/sections/5d-page-local-classes.md, a test. Risks: the message must not shift layout when it appears more than the old note did. Fits: a builder (mason).