configmap: POOL_SIZE=10 for vav-pipeline

The DBaaS (Aiven hobbyist-2, shared with Gitea) has refused
connections continuously since at least 2026-10-14 18:00Z ("remaining
connection slots are reserved for roles with the SUPERUSER
attribute"): a pool of 20 fills the ceiling by itself. Between 11:00Z
and 15:00Z today the pod held all 20 and Aiven's own monitor was
refused every 20 s; after an Aiven management-agent session opened at
11:06Z and stayed, every pod since gets 19 and one pool worker loops.
Ten connections are ample for a single replica. Needs the transmitter
to apply (kubectl apply is denied for the builder).

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

deploy/k8s/configmap.yaml

@@ -60,3 +60,11 @@ data:
 
   # Pipeline latency budget (ms) — Construction spec §2.5
   PIPELINE_LATENCY_BUDGET_MS: "5000"
+
+  # Ecto pool size for vav-pipeline (runtime.exs default 20). The DBaaS
+  # is an Aiven hobbyist-2 shared with Gitea and Aiven's own monitor;
+  # a pool of 20 fills its connection ceiling by itself (2026-10-15:
+  # refusals "remaining connection slots are reserved" for 24 h, one
+  # pool worker looping, Aiven's monitor refused). Ten is ample for a
+  # single replica.
+  POOL_SIZE: "10"