Cut over ArgoCD to Gitea: update all repoURLs and PR generator

Switch app-of-apps, platform, apps, and previews ApplicationSets
to read from in-cluster Gitea (gitea-helm-ssh.platform.svc:2222).
Previews now use Gitea PR generator instead of GitHub.

infra/kubernetes/argocd/appsets/previews.yaml

@@ -8,9 +8,13 @@ spec:
   goTemplateOptions: ["missingkey=error"]
   generators:
     - pullRequest:
-        github:
+        gitea:
           owner: lazorgurl
           repo: homelab
+          api: http://gitea-helm-http.platform.svc:3000
+          tokenRef:
+            secretName: argocd-gitea-token
+            key: token
         requeueAfterSeconds: 60
   template:
     metadata:
@@ -18,7 +22,7 @@ spec:
     spec:
       project: default
       source:
-        repoURL: git@github.com:lazorgurl/homelab.git
+        repoURL: ssh://git@gitea-helm-ssh.platform.svc:2222/lazorgurl/homelab.git
         targetRevision: "{{ .branch }}"
         path: apps/*/k8s/overlays/preview
         kustomize: