refactor: remove lite variant, fix release workflow

- Remove all lite/full variant logic from frontend, API, shared constants,
  docs, and tests (single unified Docker image only)
- Replace single QEMU multi-arch Docker build with per-architecture native
  builds (amd64 + arm64) and manifest merge to fix disk space exhaustion
- Add disk cleanup step and per-platform build cache scopes
- Switch release trigger from push to workflow_dispatch
- Add GitHub issue templates and PR template

.github/workflows/release.yml

@@ -1,8 +1,7 @@
 name: Release
 
 on:
-  push:
-    branches: [main]
+  workflow_dispatch:
 
 permissions:
   contents: write
@@ -14,7 +13,6 @@ jobs:
   release:
     name: Semantic Release
     runs-on: ubuntu-latest
-    if: "!contains(github.event.head_commit.message, '[skip ci]')"
     outputs:
       new_version: ${{ steps.check.outputs.version }}
     steps:
@@ -46,14 +44,36 @@ jobs:
         run: |
           if [ -f .release-version ]; then
             echo "version=$(cat .release-version)" >> "$GITHUB_OUTPUT"
+          else
+            echo "::error::semantic-release did not produce a new version. No releasable commits found."
+            exit 1
           fi
 
   docker:
-    name: Docker Build & Push
+    name: Build (${{ matrix.platform }})
     needs: release
-    if: needs.release.outputs.new_version != ''
-    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - platform: linux/amd64
+            runner: ubuntu-latest
+          - platform: linux/arm64
+            runner: ubuntu-24.04-arm
+    runs-on: ${{ matrix.runner }}
     steps:
+      - name: Free disk space
+        run: |
+          sudo rm -rf /usr/share/dotnet /usr/local/lib/android /opt/ghc \
+            /usr/local/share/boost /opt/hostedtoolcache/CodeQL
+          sudo docker system prune -af
+          df -h /
+
+      - name: Prepare
+        run: |
+          platform=${{ matrix.platform }}
+          echo "PLATFORM_PAIR=${platform//\//-}" >> $GITHUB_ENV
+
       - name: Checkout release tag
         uses: actions/checkout@v4
         with:
@@ -62,8 +82,64 @@ jobs:
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
 
-      - name: Set up QEMU
-        uses: docker/setup-qemu-action@v3
+      - name: Log in to Docker Hub
+        uses: docker/login-action@v3
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+
+      - name: Log in to GitHub Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: |
+            stirlingimage/stirling-image
+            ghcr.io/${{ github.repository }}
+
+      - name: Build and push by digest
+        id: build
+        uses: docker/build-push-action@v6
+        with:
+          context: .
+          file: docker/Dockerfile
+          platforms: ${{ matrix.platform }}
+          labels: ${{ steps.meta.outputs.labels }}
+          outputs: type=image,"name=stirlingimage/stirling-image,ghcr.io/${{ github.repository }}",push-by-digest=true,name-canonical=true,push=true
+          cache-from: type=gha,scope=${{ env.PLATFORM_PAIR }}
+          cache-to: type=gha,mode=max,scope=${{ env.PLATFORM_PAIR }}
+
+      - name: Export digest
+        run: |
+          mkdir -p /tmp/digests
+          digest="${{ steps.build.outputs.digest }}"
+          touch "/tmp/digests/${digest#sha256:}"
+
+      - name: Upload digest
+        uses: actions/upload-artifact@v4
+        with:
+          name: digests-${{ env.PLATFORM_PAIR }}
+          path: /tmp/digests/*
+          if-no-files-found: error
+          retention-days: 1
+
+  manifest:
+    name: Create Multi-Arch Manifests
+    needs: [release, docker]
+    runs-on: ubuntu-latest
+    steps:
+      - name: Download digests
+        uses: actions/download-artifact@v4
+        with:
+          path: /tmp/digests
+          pattern: digests-*
+          merge-multiple: true
 
       - name: Log in to Docker Hub
         uses: docker/login-action@v3
@@ -91,14 +167,16 @@ jobs:
             type=semver,pattern={{major}},value=v${{ needs.release.outputs.new_version }}
             type=raw,value=latest
 
-      - name: Build and push
-        uses: docker/build-push-action@v6
-        with:
-          context: .
-          file: docker/Dockerfile
-          push: true
-          platforms: linux/amd64,linux/arm64
-          tags: ${{ steps.meta.outputs.tags }}
-          labels: ${{ steps.meta.outputs.labels }}
-          cache-from: type=gha,scope=unified
-          cache-to: type=gha,mode=max,scope=unified
+      - name: Create Docker Hub manifest
+        working-directory: /tmp/digests
+        run: |
+          docker buildx imagetools create \
+            $(jq -cr '.tags | map(select(startswith("stirlingimage/")) | "-t " + .) | join(" ")' <<< "$DOCKER_METADATA_OUTPUT_JSON") \
+            $(printf 'stirlingimage/stirling-image@sha256:%s ' *)
+
+      - name: Create GHCR manifest
+        working-directory: /tmp/digests
+        run: |
+          docker buildx imagetools create \
+            $(jq -cr '.tags | map(select(startswith("ghcr.io/")) | "-t " + .) | join(" ")' <<< "$DOCKER_METADATA_OUTPUT_JSON") \
+            $(printf 'ghcr.io/${{ github.repository }}@sha256:%s ' *)