Build the admin History tab: filters, day-grouped rows, stats, footer

Task 9b9188b8. Adds a typed client for GET /api/v1/admin/history and the
History screen (ADMIN-SPEC §5): All events / Reversals / Missed chips that
re-query the API, per-period On time / Completed / Missed stats, rows
grouped by local day with event type, actor and on-time flag, the
append-only footer strip, an inert CSV button (TODO e5133d0f) and the
92px scroll-column padding. Wires the tab into the shell.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

admin/src/App.test.tsx

@@ -29,9 +29,8 @@ describe("NestQuest Admin shell", () => {
 
     fireEvent.click(screen.getByRole("tab", { name: "History" }));
 
-    expect(screen.getByRole("tabpanel").textContent).toContain(
-      "History placeholder",
-    );
+    expect(screen.getByRole("heading", { name: "History" })).toBeTruthy();
+    expect(screen.getByRole("tabpanel").textContent).not.toContain("placeholder");
     expect(screen.getByRole("tab", { name: "History" }).getAttribute("aria-selected")).toBe(
       "true",
     );