fix(ci): replace docker:24-cli with alpine + docker-cli in build-images

act_runner v0.3.1 has special-case handling for images named docker:*:
it automatically adds /var/run/docker.sock to the container's bind
mounts. The runner's own global config already mounts the socket, so
the two entries collide and the container fails to start with
"Duplicate mount point: /var/run/docker.sock".

Fix: use alpine:latest (no special handling) and install docker-cli
via apk alongside git in each Checkout step. The docker socket is
still available via the runner's global bind — we just stop triggering
the duplicate.

.gitea/workflows/build-images.yml

@@ -37,11 +37,11 @@ jobs:
   linux-amd64:
     runs-on: linux-amd64
     container:
-      image: docker:24-cli
+      image: alpine:latest
     steps:
       - name: Checkout
         run: |
-          apk add --no-cache git
+          apk add --no-cache git docker-cli
           git init
           git remote add origin http://172.0.0.29:3000/sarman/tftsr-devops_investigation.git
           git fetch --depth=1 origin "$GITHUB_SHA"
@@ -60,11 +60,11 @@ jobs:
   windows-cross:
     runs-on: linux-amd64
     container:
-      image: docker:24-cli
+      image: alpine:latest
     steps:
       - name: Checkout
         run: |
-          apk add --no-cache git
+          apk add --no-cache git docker-cli
           git init
           git remote add origin http://172.0.0.29:3000/sarman/tftsr-devops_investigation.git
           git fetch --depth=1 origin "$GITHUB_SHA"
@@ -83,11 +83,11 @@ jobs:
   linux-arm64:
     runs-on: linux-amd64
     container:
-      image: docker:24-cli
+      image: alpine:latest
     steps:
       - name: Checkout
         run: |
-          apk add --no-cache git
+          apk add --no-cache git docker-cli
           git init
           git remote add origin http://172.0.0.29:3000/sarman/tftsr-devops_investigation.git
           git fetch --depth=1 origin "$GITHUB_SHA"