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.tsx

@@ -24,13 +24,14 @@ import { qk } from "../lib/queryKeys";
 import { useDebounced } from "../lib/useDebounced";
 import { useUrlMirror } from "../lib/useUrlMirror";
 import LogLine from "./LogLine";
+import NavGrid from "./ui/NavGrid";
 import { Button } from "./ui/Button";
 import FilterChipGroup from "./ui/FilterChipGroup";
 import FilterSelect from "./ui/FilterSelect";
 import { Section } from "./ui/form";
 import { LoadingState, StateMessage } from "./ui/QueryState";
 
-// Admin → Diagnosztika: the server's stored log (`log_events`, E22.6). One list, newest first; a line
+// Admin → Szervernapló: the server's stored log (`log_events`, E22.6). One list, newest first; a line
 // opens in place to its full record, and its request id / job id narrow the list to that request or
 // job. Filters live in the URL, so a filtered view is a link. "Élő" re-reads the newest page every
 // few seconds while the tab is visible — the newest page only: live is watching the top, so paging
@@ -287,25 +288,28 @@ export default function AdminLogs() {
                 {t("adminLogs.empty")}
               </p>
             ) : (
-              rows.map((row) => (
-                <LogLine
-                  key={row.id}
-                  ts={row.ts}
-                  level={row.level}
-                  event={row.event ?? "—"}
-                  msg={row.msg}
-                  title={new Date(row.ts).toLocaleString()}
-                  open={open === row.id}
-                  onToggle={() => setOpen(open === row.id ? null : row.id)}
-                >
-                  <RowDetail
-                    row={row}
-                    account={row.user_id === null ? null : accountLabel(String(row.user_id))}
-                    onRequest={(requestId) => pivot({ requestId, jobId: null })}
-                    onJob={(jobId) => pivot({ requestId: null, jobId })}
-                  />
-                </LogLine>
-              ))
+              <NavGrid>
+                {rows.map((row, index) => (
+                  <LogLine
+                    navIndex={index}
+                    key={row.id}
+                    ts={row.ts}
+                    level={row.level}
+                    event={row.event ?? "—"}
+                    msg={row.msg}
+                    title={new Date(row.ts).toLocaleString()}
+                    open={open === row.id}
+                    onToggle={() => setOpen(open === row.id ? null : row.id)}
+                  >
+                    <RowDetail
+                      row={row}
+                      account={row.user_id === null ? null : accountLabel(String(row.user_id))}
+                      onRequest={(requestId) => pivot({ requestId, jobId: null })}
+                      onJob={(jobId) => pivot({ requestId: null, jobId })}
+                    />
+                  </LogLine>
+                ))}
+              </NavGrid>
             )}
           </div>