fix(ci): build docker images on frontend-only master pushes

the docker workflow chained off the backend workflow only, and backend has a
backend/** path filter. master pushes touching just frontend/apps or the docker
files never triggered docker.yml, so no master image was published and
remark42.com was not redeployed. broken since the build workflow was split in
#1977.

listen to workflow_run from both backend and frontend, and add Dockerfile,
docker-init.sh and .dockerignore to the backend workflow paths to restore the
path coverage the old build workflow had.

.github/workflows/ci-backend.yml

@@ -7,6 +7,9 @@ on:
     paths:
       - ".github/workflows/ci-backend.yml"
       - "backend/**"
+      - "Dockerfile"
+      - "docker-init.sh"
+      - ".dockerignore"
       - "!backend/scripts/**"
       - "!**.md"
   pull_request:
@@ -14,6 +17,9 @@ on:
     paths:
       - ".github/workflows/ci-backend.yml"
       - "backend/**"
+      - "Dockerfile"
+      - "docker-init.sh"
+      - ".dockerignore"
       - "!backend/scripts/**"
       - "!**.md"
 

.github/workflows/docker.yml

@@ -2,7 +2,7 @@ name: docker
 
 on:
   workflow_run:
-    workflows: [backend]
+    workflows: [backend, frontend]
     types: [completed]
 
 concurrency: