feat(diagnostics): walk the log lines from the keyboard; name the console "Server log"

Both log viewers put their lines in a NavGrid: j/k (and the arrows) step
from line to line, and Enter opens one exactly as a click does (the line's
button is its `data-nav-open`). A focused line is named by its code and
message.

The console's nav entry is "Szervernapló" / "Server log", its page title:
"Diagnosztika" was already the Settings tab that holds the user's own log,
and two places with one name read as one place.

frontend/src/components/AdminLogs.dom.test.tsx

@@ -142,6 +142,17 @@ describe("AdminLogs", () => {
     ).toBe("true");
   });
 
+  it("the keyboard can walk the lines and open one (NavGrid items)", async () => {
+    logsMock.mockResolvedValue({ items: [row(2), row(1)], accounts: {}, next_cursor: null });
+    renderConsole();
+    await waitFor(() => expect(lines()).toHaveLength(2));
+
+    const items = lines().map((b) => b.parentElement!);
+    expect(items.map((el) => el.getAttribute("data-nav-index"))).toEqual(["0", "1"]);
+    expect(lines().every((b) => b.hasAttribute("data-nav-open"))).toBe(true);
+    expect(screen.getByTestId("admin-logs-lines").querySelector("[data-nav-list]")).toBeTruthy();
+  });
+
   it("a failed read is an error with a retry, not an empty log", async () => {
     logsMock.mockRejectedValue(new Error("502"));
     renderConsole();