Lighten the client shell and finish four client surfaces

- Load each settings section on its own: the section route imported all
  twenty-one statically. A preload starts the chunk beside the record
  gate's read, and the loading state paints the settings card shell.
  /settings/[section] goes from 611 to 403 KB gz.
- Take Zod out of the shell every route shares: the account-access parse
  run on each boot is plain TypeScript now, held to the published schema
  by an equivalence test over good and broken blocks. The canonical unit
  table moves to its own module, so the display transform no longer
  pulls Zod in either. Layout entry 199 to 136 KB gz; /insights 369 to
  304, /medications 428 to 365, /labs 400 to 337.
- Open a saved Coach conversation at its last answer: an instant jump
  instead of the smooth scroll that lost the end, then follow late
  layout (charts, tables) for a few seconds until the reader scrolls.
- Show the document archive as a month grid of preview tiles, two
  across on a phone and three or four on a desktop, with the month
  headings kept.
- Add the admin card for the measurement table maintenance: a status
  read on the maintenance route, one calm confirmation, and the run's
  state while it is queued, running, finished or stopped.
- Re-base the bundle budget: /insights at 304, /settings/[section]
  watched at 403, aggregate cap 4335 with the reason written down.

src/app/admin/[section]/renderer.tsx

@@ -5,7 +5,7 @@
  * a given slug. Lives next to the route page so the shell can stay a
  * server component while the auth-gated body remains a client component.
  *
- * This is the equivalent of `SECTION_COMPONENTS` in
+ * This is the equivalent of `SettingsSectionLoader` for
  * `src/app/settings/[section]/page.tsx`, lifted to a separate file so
  * the route page can be a server component (Settings can keep
  * `"use client"`-leaning components in its page because none of them
@@ -36,6 +36,7 @@ import { ModuleAvailabilitySection } from "@/components/admin/module-availabilit
 import { RemindersSection } from "@/components/admin/reminders-section";
 import { ServicesSection } from "@/components/admin/services-section";
 import { SystemStatusSection } from "@/components/admin/system-status-section";
+import { MeasurementMaintenanceCard } from "@/components/admin/measurement-maintenance-card";
 import { InviteTokensSection } from "@/components/admin/invite-tokens-section";
 import { UserManagementSection } from "@/components/admin/user-management-section";
 import type { AdminSectionSlug } from "@/components/admin/section-slugs";
@@ -60,6 +61,8 @@ export function AdminSectionRenderer({
       return (
         <SectionFrame>
           <SystemStatusSection />
+          {/* v1.42 — the table maintenance after the tombstone purge. */}
+          <MeasurementMaintenanceCard />
         </SectionFrame>
       );
     case "general":