fix(observability): 🐛 fix Vector log shipping URL on all clusters

Restores missing '.buildth.ing' domain segment in Vector elasticsearch
endpoint for benchmark, dev, and edp instances.

Template source uses {{{ .Env.DOMAIN_O12Y }}} (correct) — instances
were mis-hydrated, omitting the TLD suffix.

otc/dev.t09.de/stacks/observability-client/vector/values.yaml

@@ -48,7 +48,7 @@ customConfig:
       type: elasticsearch
       inputs: [parser]
       endpoints: 
-        - https://o12y.observability./insert/elasticsearch/
+        - https://o12y.observability.buildth.ing/insert/elasticsearch/
       auth:
         strategy: basic
         user: ${VECTOR_USER}