Frontend: communication preferences UI

[dgee2]

Goal

Give users a preferences settings page where they can toggle communication categories.

Spec reference

docs/specs/recipe-creation-target-architecture.md — §"Related recipe usage capabilities – Communication preferences"

Implementation notes

• New authenticated route /settings/preferences
• PreferencesPage.vue: list of category toggles with human-readable labels (e.g. "Publication approvals", "Share and access changes")
• useCommunicationPreferences composable wrapping GET/PUT endpoints
• Regenerate OpenAPI types: pnpm generate-openapi

Acceptance criteria

• All categories rendered with current state
• Toggle saves immediately via PUT

Testing

• Vitest: useCommunicationPreferences composable (load, toggle)
• Vitest: PreferencesPage renders all category toggles

Part of#1108