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/schema.ts

@@ -87,6 +87,25 @@ export const householdMembers = pgTable(
   (t) => [primaryKey({ columns: [t.householdId, t.userId] })],
 );
 
+export const activityLog = pgTable(
+  "activity_log",
+  {
+    id: uuid("id").primaryKey().defaultRandom(),
+    householdId: uuid("household_id")
+      .notNull()
+      .references(() => households.id, { onDelete: "cascade" }),
+    entityType: text("entity_type").notNull(),
+    entityId: uuid("entity_id").notNull(),
+    actorId: uuid("actor_id")
+      .notNull()
+      .references(() => users.id, { onDelete: "cascade" }),
+    action: text("action").notNull(),
+    payload: jsonb("payload").$type<Record<string, unknown> | null>(),
+    createdAt: timestamp("created_at", { withTimezone: true }).notNull().defaultNow(),
+  },
+  (t) => [index("activity_log_household_created_idx").on(t.householdId, t.createdAt)],
+);
+
 export const reminders = pgTable(
   "reminders",
   {