feat(ui): Disk, Traefik, UniFi and Settings say things plainly (#5212)

#5212 "Plain labels: no raw ids, scopes, metric keys or unexplained jargon",
batch 3:

- Disk page: each tile says what it holds. "Writable layers" becomes
  "Container files" and Build cache says it is safe to clear. Shared is
  "Shared with other images" with a tooltip, and "dangling" is gone.
  Untagged images show by id instead of "<none>", a capped list says
  "The 50 largest of N images", and each host shows "as of" its report.
- Traefik: an expired certificate reads "expired 12 days ago", not "-12
  days" (cert_left). The Traffic empty state knows whether the access log
  is on: off points to Settings → Plugins → Traefik; on says to check the
  mounted log path.
- Moments use |ago with an exact UTC tooltip: UniFi last seen, alarms,
  events, speed test and DPI; AI token last used.
- Settings: the Auth tab is "Authentication" like its breadcrumb, plugin
  fields read "Metrics URL" not metrics_url (field_label), a source's pull
  interval is "every 1h", and the last report time drops the ISO "T".

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

plugins/traefik/routes.py

@@ -85,14 +85,17 @@ def split_routers(routers: list[dict]) -> tuple[list[dict], list[dict]]:
     return problems, healthy
 
 
+def _access_log() -> dict:
+    """The plugin's access_log settings ({} when unset or malformed)."""
+    cfg = current_app.config["PLUGINS"]["traefik"].get("access_log", {})
+    return cfg if isinstance(cfg, dict) else {}
+
+
 @traefik_bp.get("/")
 @require_role(UserRole.viewer)
 async def index():
     poll_interval = current_app.config.get("MONITORS_POLL_INTERVAL", 60)
-    _al_cfg = current_app.config["PLUGINS"]["traefik"].get("access_log", {})
-    if not isinstance(_al_cfg, dict):
-        _al_cfg = {}
-    access_log_enabled = _al_cfg.get("enabled", False)
+    access_log_enabled = bool(_access_log().get("enabled", False))
     current_range = request.args.get("range", DEFAULT_RANGE)
     return await render_template(
         "traefik/index.html",
@@ -368,8 +371,10 @@ async def traffic():
         rows = result.scalars().all()
 
     if not rows:
+        al = _access_log()
         return await render_template(
-            "traefik/traffic.html", summary=None, history=[], range_key=range_key
+            "traefik/traffic.html", summary=None, history=[], range_key=range_key,
+            access_log_enabled=bool(al.get("enabled", False)), access_log_path=al.get("path", ""),
         )
 
     total = sum(r.total_requests for r in rows)