ci: add Gitea ROCm server image build workflow

Build the server-rocm image locally on Gitea Runner instead of pulling
from ghcr.io. Narrows GPU arch targets to gfx1100-1102 (Navi 31/32/33)
for faster builds and smaller images.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.github/workflows/build-rocm.yml

@@ -0,0 +1,42 @@
+name: Build ROCm Server Image
+
+on:
+  workflow_dispatch:
+  push:
+    paths:
+      - '.devops/rocm.Dockerfile'
+      - '.github/workflows/build-rocm.yml'
+
+jobs:
+  build-rocm-server:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Determine build tag
+        id: tag
+        run: |
+          # Use short commit hash as build number (matches upstream bXXXX convention)
+          BUILD_NUM="b$(git rev-list --count HEAD)"
+          echo "build_num=${BUILD_NUM}" >> $GITHUB_OUTPUT
+          echo "Build number: ${BUILD_NUM}"
+
+      - name: Log in to Gitea Container Registry
+        run: |
+          echo "${{ github.token }}" | docker login git.wylab.me -u ${{ github.actor }} --password-stdin
+
+      - name: Build server-rocm image
+        run: |
+          docker build \
+            --target server \
+            --build-arg ROCM_DOCKER_ARCH='gfx1100;gfx1101;gfx1102' \
+            -f .devops/rocm.Dockerfile \
+            -t git.wylab.me/wylab/llama.cpp:server-rocm-${{ steps.tag.outputs.build_num }} \
+            -t git.wylab.me/wylab/llama.cpp:server-rocm \
+            .
+
+      - name: Push images
+        run: |
+          docker push git.wylab.me/wylab/llama.cpp:server-rocm-${{ steps.tag.outputs.build_num }}
+          docker push git.wylab.me/wylab/llama.cpp:server-rocm