feat(postgres): upgrade shared database to PostgreSQL 17

Move the shared postgres service from 15.19 to 17.6 as the postgres17 StatefulSet with its own PVC, extend the initdb and ingress policy with the statuspage database, and drop the now-unused per-app postgres manifests for authentik, gitea and netronome.

postgres/k8s/secrets.yaml.example

@@ -10,3 +10,4 @@ stringData:
   GITEA_DB_PASSWORD: ""
   NETRONOME_DB_PASSWORD: ""
   PENPOT_DB_PASSWORD: ""
+  STATUSPAGE_DB_PASSWORD: ""