feat(infra): Objecten API up in compose, wired to Objecttypen (refs #140)

Stands up the upstream Maykin Objecten API in the stack — own PostGIS DB
+ redis, an -init that runs setup_configuration from the external config
volume (migrate + provision a static token + register the Objecttypen API
as a trusted service), and a health-checked web on host :8021. Objecten's
setup_configuration registers Objecttypen (api_type orc, api_key auth with
the S-18a dev token) so an object can reference its objecttype.

Same verbatim-image + seed-config pattern as S-18a. Wired into WAIT_SVCS,
CFG_VOLS, the SEED invocations, seed-config.sh, and the CI log-dump. Pinned
objects-api 3.4.0 (nearest release to objecttypes-api 3.4.2).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

infra/seed-config.sh

@@ -13,7 +13,7 @@
 # subcommand. Fixed-name `external` volumes keep the names deterministic across
 # both runtimes. See docs/runbooks/gitea-actions-gotchas.md.
 #
-# Usage: seed-config.sh <key> [<key> ...]   where key ∈ { oz, kc, fl }
+# Usage: seed-config.sh <key> [<key> ...]   where key ∈ { oz, nrc, kc, fl, objecttypen, objecten }
 set -euo pipefail
 
 here="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
@@ -33,7 +33,7 @@ populate() {  # volume  source(file or dir/.)
   echo "  seeded $vol"
 }
 
-[ "$#" -gt 0 ] || { echo "usage: seed-config.sh <oz|nrc|kc|fl|objecttypen> ..." >&2; exit 2; }
+[ "$#" -gt 0 ] || { echo "usage: seed-config.sh <oz|nrc|kc|fl|objecttypen|objecten> ..." >&2; exit 2; }
 
 # The registratie process (BPMN) and its diploma-eligibility DMN are deployed as SEPARATE Flowable
 # deployments — the process engine and the DMN engine each own theirs (S-13, ADR-0016). flowable-rest
@@ -50,6 +50,7 @@ for key in "$@"; do
     nrc) populate rr-nrc-config "$here/opennotificaties/setup_configuration/." ;;
     kc) populate rr-kc-realms "$here/keycloak/realms/." ;;
     objecttypen) populate rr-objecttypen-config "$here/objecttypen/setup_configuration/." ;;
+    objecten) populate rr-objecten-config "$here/objecten/setup_configuration/." ;;
     fl) d="$(mktemp -d)"; stage_flowable_workflows "$d"; populate rr-fl-bpmn "$d/." ;;
     *)  echo "unknown seed key: $key" >&2; exit 2 ;;
   esac