fix(observability): 🐛 fix remote write URL and add manifests for benchmark + edp clients

- Fix broken remote write URL (o12y.observability./ → o12y.observability.buildth.ing/)
- Create manifests/ dirs with .gitkeep for benchmark.t09.de and edp.buildth.ing
- Copy forgejo-scrape.yaml VMServiceScrape manifest to both instances

otc/benchmark.t09.de/stacks/observability-client/vm-client-stack/manifests/forgejo-scrape.yaml

@@ -0,0 +1,15 @@
+apiVersion: operator.victoriametrics.com/v1beta1
+kind: VMServiceScrape
+metadata:
+  name: forgejo
+  namespace: observability
+spec:
+  namespaceSelector:
+    matchNames:
+      - gitea
+  selector:
+    matchLabels:
+      app.kubernetes.io/name: forgejo
+  endpoints:
+    - port: http
+      path: /metrics