refactor(admin): the console speaks the Settings vocabulary without an accent

Twenty-six of twenty-eight admin files already used the Settings card and
header. What made the console read as its own system was everything on top of
that: three hand-rolled cards, a header slot that meant five different things,
and a heading the frame took but never painted.

- `SectionFrame` drops `title` and `subtitle`. Seventeen call sites passed
  both into a component that has rendered neither since v1.18.6.1 — the shell
  reads the same keys itself. A prop contract nothing honours is a promise the
  next reader believes.
- The invite card, the four host-metric headers, and the `/admin` welcome
  card stop hand-rolling `bg-card border rounded-xl` shells with their own
  padding steps and their own heading weights. `text-sm` as a card title on
  the first card of a page, directly above a correct one, was the first thing
  the eye landed on.
- The header status slot carries status. The backups run, the invite create,
  the danger-zone wipe, and the user filters come out of it; the app-log
  refresh stays but reads as the secondary it is.
- Loading states paint their card and header. Encryption returned a bare
  spinner row and then a card, so the section jumped when the status landed —
  the fix `coach-feedback-section.tsx` already carried, applied where it was
  missing. Same for the notification-status card.
- One label/value tile. `StatusItem`, the encryption section's private `Stat`,
  the user-management inline panels and the backups upload box were four
  fills and three paddings for one role.
- The overview stopped printing the running version, build SHA and build time
  twice, thirty pixels apart. The version tile owns build identity — it is the
  one that checks for a newer release; the snapshot owns what is running.
- `ai-server-key` had three paragraphs stacked in a muted `text-xs` slot;
  one sentence stays there and the two that carry information move into the
  body as foreground. The central-codex consent copy moves the same way, and
  its disconnect is `variant="destructive"` — which `ConfirmButton` refused to
  accept, so every destructive confirm in the tree had been hand-tinting an
  outline instead.
- Leftovers: the `-mt-2` correcting the card's own rhythm, two alpha hovers on
  text, `text-[10px]` badges, the redundant `space-y-6` wrapper, the empty
  state repeating the header's CTA, and the `mt-6` a card added inside a
  frame that already spaces its children.

src/components/admin/__tests__/status-card-grid.test.tsx

@@ -6,7 +6,10 @@ import { renderToStaticMarkup } from "react-dom/server";
  * `StatusCardGrid` (the section-card grid the maintainer described as redundant
  * with the sidebar nav). The status-card component itself was removed
  * from the codebase. This test guards the *new* overview composition:
- * a welcome card, the system snapshot, and the recent-audit preview.
+ * the version tile, the system snapshot, and the recent-audit preview. The
+ * welcome card went with the grid: it greeted the reader and told them they
+ * were signed in as an administrator, on a route only an administrator can
+ * reach.
  *
  * The file kept its old name so git history follows it. Nothing else
  * imports `status-card-grid`.
@@ -71,12 +74,10 @@ describe("/admin overview composition", () => {
     expect(html).not.toContain("Open backups");
   });
 
-  it("renders the welcome card with the admin's username", () => {
+  it("renders no welcome card", () => {
     const html = render(<AdminOverviewPage />);
-    // `welcomeTitle` interpolates the username; the mocked auth hook
-    // returns "testuser".
-    expect(html).toContain("Welcome, testuser");
-    expect(html).toContain("admin-overview-welcome-heading");
+    expect(html).not.toContain("Welcome, testuser");
+    expect(html).not.toContain("admin-overview-welcome-heading");
   });
 
   it("renders the system snapshot section heading", () => {