Releases: tag each healthy deploy vMAJOR.MINOR.PATCH; /health and node checkin report versions (node-26#49)

VERSION holds MAJOR.MINOR (1.1). The build job works out the next patch
(scripts/next-version.sh, integer count) and stamps it into c2-core as
DRB_VERSION, which /health returns. The new "Tag release" job tags the
commit only after the deploy job succeeds, so a failed deploy's number is
reused. Node checkins carry `version`, stored on the node doc.

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

drb-c2-core/app/main.py

@@ -187,6 +187,7 @@ app.include_router(discord_oauth.router)  # auth per-endpoint (org owner / signe
 # build stamp baked in by the Dockerfile, not configuration anyone sets or
 # tunes, and keeping it out of Settings avoids implying it can be changed.
 _GIT_SHA = os.getenv("GIT_SHA", "unknown")
+_VERSION = os.getenv("DRB_VERSION", "untagged")
 
 
 @app.get("/health")
@@ -197,6 +198,7 @@ async def health():
         # CI asserts this equals the commit it just deployed. Without it a
         # deploy can "succeed" while the previous container is still serving.
         "git_sha": _GIT_SHA,
+        "version": _VERSION,
     }