Settings form errors use the shared component, and the page-local .error-note class is gone #7760

For: P0 Trust, specifically one design system with no page-local classes.

Today .error-note is a page-local class: its rule is in src/web/style/components.ts (around line 144), it is used twice in src/web/pages/account.ts (the notify URL form near line 117, and near line 854), and it is named in docs/design/sections/5d-page-local-classes.md.

Done looks like:

• [ ] Both messages in src/web/pages/account.ts draw an existing shared component in the danger tone, the one other forms use for a refused submit (look in src/web/ui.ts and src/web/flash.ts). Do not add a new class. The words stay the same and are still escaped.
• [ ] grep -rn error-note src docs finds nothing: the rule leaves components.ts and the name leaves §5d.
• [ ] A test posts an invalid notify URL to /settings/notify and finds the message in the shared component's markup. It fails without the change.
• [ ] 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, one test. Risks: do not change the notify URL validation itself.

Deferred behind the Later gate (#595). The forge parks this work because the same change, #5218, was dropped. Until a person decides .error-note should go after all, this cleanup waits rather than taking a builder slot.

Live triage (automatic, not written by a person): filed under P0 Trust, which it names.