Implement share viewer (task 31)

- Makes actorId nullable in activity_log (migration 0010) with onDelete:
  set null so audit history survives user deletion; adds logShareActivity
  for anonymous mutations
- Adds resolveShareToken return of householdId for downstream validation
- Adds renderSharedView to EntityTypeRegistration; each module implements
  loadForShare (no-session bare queries) and renderSharedView
- Calendar: CalendarSharedView (upcoming 90-day events) and
  EventSharedView (title/time/location/notes)
- Lists: ListSharedView (client component with optimistic toggles via
  toggleShareListItem server action in lists/server/share-actions.ts)
- Notes: NoteSharedView (title + body + updated date)
- /app/s/[token]/page.tsx: resolves token, dispatches to loadForShare +
  renderSharedView, friendly error for invalid/expired tokens, noindex
- Middleware /s/* exemption confirmed present (no change needed)

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

src/modules/_core/index.ts

@@ -12,6 +12,6 @@ export type {
 } from "./module";
 export { registerModule, getRegistry, getEntityType, getWidget, getQuickAdds } from "./registry";
 export type { QuickAddItem, SerializedQuickAddItem } from "./registry";
-export { logActivity } from "./activity";
+export { logActivity, logShareActivity } from "./activity";
 export { createShareLink, resolveShareToken, revokeShareLink } from "./share";
 export type { ShareLinkCapabilities, CreateShareLinkResult } from "./share";