Fix meet: ALLOWED_HOSTS, OIDC callback, and LiveKit connectivity

- meet-config: rename ALLOWED_HOSTS → DJANGO_ALLOWED_HOSTS (django-configurations
  ListValue uses DJANGO_ prefix by default; without it the list was empty and
  every browser request got 400 DisallowedHost)
- meet-config: set LIVEKIT_API_URL to public https://livekit.DOMAIN_SUFFIX so
  the meet frontend can reach LiveKit for WebSocket signaling
- pingora-config: add livekit.DOMAIN_SUFFIX → livekit-server:80 WebSocket route
- cert-manager: add livekit.DOMAIN_SUFFIX to TLS cert dnsNames
- oidc-clients: fix meet redirect URI /oidc/callback/ → /api/v1.0/callback/
  (meet embeds mozilla-django-oidc inside the api/v1.0/ prefix); add
  postLogoutRedirectUri for clean logout
- livekit-values: replace hardcoded devkey:secret-placeholder with key_file
  loaded from a VSO-managed K8s Secret (secret/livekit in OpenBao)
- media/vault-secrets: add VaultAuth + VaultStaticSecret for media namespace
  to sync livekit API credentials from OpenBao

base/ingress/pingora-config.yaml

@@ -156,6 +156,11 @@ data:
     host_prefix = "grafana"
     backend     = "http://kube-prometheus-stack-grafana.monitoring.svc.cluster.local:80"
 
+    [[routes]]
+    host_prefix = "livekit"
+    backend     = "http://livekit-server.media.svc.cluster.local:80"
+    websocket   = true
+
     [[routes]]
     host_prefix = "s3"
     backend     = "http://seaweedfs-filer.storage.svc.cluster.local:8333"