fix(traefik): a renewed certificate is old, and list_certificates is bounded (#5864)

A Traefik that hasn't restarted keeps reporting the certificate it
replaced, so codex.fabledsword.com's old one (21 days left) was listed
beside its renewal (81 days) and would have raised an expiry warning on
2026-10-22. A reported certificate whose every name a later-expiring
one covers is now old, on the page, the widget, the overview and MCP.

list_certificates takes `limit` (default 100) with total/truncated, and
says how many served certificates no HTTP router uses (`unrouted`).

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

docs/plugins/traefik.md

@@ -103,7 +103,7 @@ The full Traefik page at `/plugins/traefik/` reads top to bottom, for the time r
    - **Slow responses** compare p95 with p50. When p95 is 4× p50 or more, a few requests are slow (one endpoint or a heavy page). When p50 is close behind, the whole app is slow.
    - **Next:** a fault links to the swarm service behind the router (its tasks and logs) when Steward can match the name ("codex@swarm" → `codex_app`, "radarr@swarm" → `arr_radarr`), otherwise to Docker → Swarm. Traffic links to Settings → Thresholds.
 4. **Traefik's own figures:** when its config last reloaded, open connections, memory.
-5. **The healthy routers,** folded into one table, then the routers Traefik no longer reports, then TLS certificates by soonest expiry, then Traffic Origin when the access log is on.
+5. **The healthy routers,** folded into one table, then the routers Traefik no longer reports, then TLS certificates by soonest expiry, then Traffic Origin when the access log is on. A certificate Traefik has renewed is listed as old, not by its expiry, though a Traefik that hasn't restarted since keeps reporting it: one whose every name a later-expiring certificate covers.
 
 A router is graded on its last 15 minutes against Settings → Thresholds. When a problem started is read from the router's history over the range.