Implement activity log (task 22)

- activity_log table in _core/schema.ts with household+created_at index;
  migration 0008_activity_log.sql applied
- logActivity() in _core/activity.ts reads current session and inserts a row
- ActivityLogEntry type + renderActivity?(entry): string added to
  EntityTypeRegistration so modules declare human-readable labels without
  any if/else branches in the widget
- core.activity widget replaced with a real async server component that
  queries the last 20 rows and renders via the registry
- logActivity wired into every create/update/delete in calendar, lists,
  and notes server actions; getAuthorizedItem also returns text so
  toggle/delete can include item text in the payload
- pnpm typecheck, lint, build, and all 4 E2E specs pass

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

src/modules/_core/module.ts

@@ -1,6 +1,17 @@
 import type { ReactNode } from "react";
 import type { ZodType } from "zod";
 
+export type ActivityLogEntry = {
+  id: string;
+  householdId: string;
+  entityType: string;
+  entityId: string;
+  actorId: string;
+  action: string;
+  payload: Record<string, unknown> | null;
+  createdAt: Date;
+};
+
 export type ShareCapabilities = {
   canShare: boolean;
   defaultCapabilities?: string[];
@@ -58,6 +69,7 @@ export type EntityTypeRegistration = {
   search?: SearchAdapter;
   resolveUrl: (id: string) => string;
   loadForShare?: (id: string) => Promise<unknown>;
+  renderActivity?: (entry: ActivityLogEntry) => string;
 };
 
 export type ModuleManifest = {