fix: add concurrency groups to publish workflows

Multiple CI completions for the same commit (tag push + branch push)
caused duplicate publish and docker runs. Concurrency group keyed on
head_sha ensures only one publish runs per commit.

.github/workflows/docker-publish.yml

@@ -5,6 +5,10 @@ on:
     workflows: ["CI"]
     types: [completed]
 
+concurrency:
+  group: docker-${{ github.event.workflow_run.head_sha }}
+  cancel-in-progress: true
+
 permissions:
   contents: read
   packages: write

.github/workflows/publish.yml

@@ -5,6 +5,10 @@ on:
     workflows: ["CI"]
     types: [completed]
 
+concurrency:
+  group: publish-${{ github.event.workflow_run.head_sha }}
+  cancel-in-progress: true
+
 permissions:
   contents: write
   id-token: write