dev-image arm64 build broken: pgvector apt install pulls networkd-dispatcher whose postinst fails under QEMU — blocks all releases

Release run 30495772928 (v26.07.28-01, 2026-07-29) failed at Deployment / Build/Push Docker Dev Image, which skips Release/Release-Notes/Promote-latest/Changelog downstream — every release is blocked until this is fixed.

Root cause: docker/dev-env/Dockerfile:42 runs apt install -y postgresql-$PG_VERSION-pgvector without --no-install-recommends. The recommends chain pulls networkd-dispatcher + python3-gi, whose maintainer scripts attempt systemd-resolved setup inside the container and fail on the linux/arm64 (QEMU-emulated) platform (dpkg returned an error code (1) on those two packages → apt exit 100). An Ubuntu noble package update on 2026-07-29 made this newly fatal — the same line built fine on 2026-07-27.

Fix: apt install -y --no-install-recommends postgresql-$PG_VERSION-pgvector — avoids the irrelevant network-management stack entirely (and slims the image). Not related to the SDK-pipeline testing (#36780); Kevin's from-main run hit it cold.

Start at docker/dev-env/Dockerfile:42 and inspect the PostgreSQL pgvector apt installation and its recommended packages. Verify the arm64/QEMU Docker dev-image build after excluding the failing network-management dependencies; done means the apt step succeeds and the release build can continue.