refactor: add SessionPageHeader and apply to all 6 session detail pages

- Create SessionPageHeader component (breadcrumb + editable title + collaborator + badges + date)
- Embed UPDATE_FN map internally, keyed by workshopType — no prop drilling
- Replace duplicated header blocks in sessions, motivators, year-review, weather, weekly-checkin, gif-mood

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/components/ui/index.ts

@@ -13,6 +13,7 @@ export {
   EditableGifMoodTitle,
 } from './EditableTitles';
 export { PageHeader } from './PageHeader';
+export { SessionPageHeader } from './SessionPageHeader';
 export { Input } from './Input';
 export { ParticipantInput } from './ParticipantInput';
 export { Modal, ModalFooter } from './Modal';