Pin node images to the checked-out source tree (node-26#19)

Nodes checked out v1 code but pulled :latest/:stable images built from main.
Each image is now tagged src-<git tree hash of its build directory>: CI adds
that tag in every build-*.yml, and scripts/image-tags.sh computes the same
value on the node and writes it into .env as DRB_TAG_*, which
docker-compose.yml uses (falls back to :latest/:stable for local dev).
Tree hashes stay exact even though each image only rebuilds when its own
directory changes.

- install.sh pins after checkout and fails loudly if a pinned image is
  missing (compose pull only warns for services with a build: section).
- drb-update.sh pulls the target commit's pinned images BEFORE checkout,
  using the target's own compose file, so a missing image changes nothing
  (uvicorn --reload would otherwise run new code on old images). It then
  checks out, writes the pins, recreates, and removes superseded src- tags.
- New "Release images" workflow (v* tags + manual dispatch) builds any
  src- image a release ref is missing; it skips ones already published.

The live v1 tag is not moved.

Refs #19

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docker-compose.yml

@@ -1,6 +1,10 @@
+# Image tags: a provisioned node pins every image to the source tree it has
+# checked out (DRB_TAG_* = src-<git tree hash>, written into .env by install.sh
+# and scripts/drb-update.sh via scripts/image-tags.sh — node-26#19). Unset, as
+# in local dev, they fall back to :latest / :stable, which CI builds from main.
 services:
   icecast:
-    image: ${IMAGE_REGISTRY:-git.vpn.cusano.net}/${DOCKER_ORG:-logan}/${DOCKER_REPO:-node-26}/icecast:latest
+    image: ${IMAGE_REGISTRY:-git.vpn.cusano.net}/${DOCKER_ORG:-logan}/${DOCKER_REPO:-node-26}/icecast:${DRB_TAG_ICECAST:-latest}
     build: ./icecast
     restart: unless-stopped
     network_mode: host
@@ -16,7 +20,7 @@ services:
   # rather than being exposed. edge-node still reaches both over localhost
   # because it shares this host network namespace.
   op25:
-    image: ${IMAGE_REGISTRY:-git.vpn.cusano.net}/${DOCKER_ORG:-logan}/${DOCKER_REPO:-node-26}/op25-client:stable
+    image: ${IMAGE_REGISTRY:-git.vpn.cusano.net}/${DOCKER_ORG:-logan}/${DOCKER_REPO:-node-26}/op25-client:${DRB_TAG_OP25:-stable}
     build: ./op25-container
     restart: unless-stopped
     privileged: true
@@ -38,7 +42,7 @@ services:
   # node-26#9. Same network/device access as op25 for the same reason: it
   # needs the raw USB device, not a virtualized one.
   secondary-sdr:
-    image: ${IMAGE_REGISTRY:-git.vpn.cusano.net}/${DOCKER_ORG:-logan}/${DOCKER_REPO:-node-26}/secondary-sdr:latest
+    image: ${IMAGE_REGISTRY:-git.vpn.cusano.net}/${DOCKER_ORG:-logan}/${DOCKER_REPO:-node-26}/secondary-sdr:${DRB_TAG_SECONDARY_SDR:-latest}
     build: ./secondary-sdr-container
     restart: unless-stopped
     privileged: true
@@ -48,7 +52,7 @@ services:
       - /dev:/dev
 
   edge-node:
-    image: ${IMAGE_REGISTRY:-git.vpn.cusano.net}/${DOCKER_ORG:-logan}/${DOCKER_REPO:-node-26}/edge-node:latest
+    image: ${IMAGE_REGISTRY:-git.vpn.cusano.net}/${DOCKER_ORG:-logan}/${DOCKER_REPO:-node-26}/edge-node:${DRB_TAG_EDGE_NODE:-latest}
     build: ./drb-edge-node
     restart: unless-stopped
     network_mode: host