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/module.ts

@@ -6,7 +6,7 @@ export type ActivityLogEntry = {
   householdId: string;
   entityType: string;
   entityId: string;
-  actorId: string;
+  actorId: string | null;
   action: string;
   payload: Record<string, unknown> | null;
   createdAt: Date;
@@ -69,6 +69,11 @@ export type EntityTypeRegistration = {
   search?: SearchAdapter;
   resolveUrl: (id: string) => string;
   loadForShare?: (id: string) => Promise<unknown>;
+  renderSharedView?: (props: {
+    data: unknown;
+    capabilities: { read: boolean; write: boolean };
+    token: string;
+  }) => ReactNode;
   renderActivity?: (entry: ActivityLogEntry) => string;
 };