build: migrate ingresses for Traefik v3 (k3s upgrade)

k3s update bumped Traefik chart 37 → 39, dropping v2 support. Replace
the v2-only `whitelist.sourcerange` annotation on the gitea ingress
with an `ipAllowList` Middleware (resources/gitea-middleware.yaml),
referenced via `router.middlewares`. Switch the default-ns ingresses
(kube-plex, radarr, sonarr, lidarr) from the deprecated
`kubernetes.io/ingress.class` annotation to `spec.ingressClassName`.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

resources/gitea-middleware.yaml

@@ -0,0 +1,12 @@
+---
+apiVersion: traefik.io/v1alpha1
+kind: Middleware
+metadata:
+  name: lan-only
+  namespace: gitea
+spec:
+  ipAllowList:
+    sourceRange:
+      - 192.168.0.0/16
+      - 10.0.0.0/8
+      - 172.16.0.0/12