Port postgres to Go and install the extensions a consumer asks for

letta crash-loops on 'type "vector" does not exist': pgvector is not a
trusted extension, so only the provider's superuser can create it, and
the provisioner never did. A contribution may now name extensions; the
provider creates each (IF NOT EXISTS, available ones only) in the
consumer's database on every pass. Go per the standing rule for a
TypeScript module that changes. letta asks for vector.

modules/postgres/go.mod

@@ -0,0 +1,14 @@
+module postgres
+
+go 1.25.0
+
+require (
+	git.novox.be/novox/mesh-sdk/go v0.1.7
+	github.com/jackc/pgx/v5 v5.11.0
+)
+
+require (
+	github.com/jackc/pgpassfile v1.0.0 // indirect
+	github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 // indirect
+	golang.org/x/text v0.29.0 // indirect
+)