fix: add disk cleanup to CI and reduce Docker layers

Runner runs out of disk space during discord-gateway build.
Add docker system prune before build and combine Dockerfile
layers to reduce disk usage.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.gitea/workflows/deploy.yml

@@ -20,6 +20,9 @@ jobs:
           apt-get update -qq
           apt-get install -y -qq --no-install-recommends ca-certificates git docker.io
           git config --global http.sslVerify false
+          # Clean up runner disk before build
+          docker system prune -af --volumes 2>/dev/null || true
+          apt-get clean 2>/dev/null || true
 
       - name: Checkout
         run: |

infra/docker/Dockerfile.discord-gateway

@@ -27,11 +27,12 @@ COPY packages/shared ./packages/shared
 COPY services/discord-gateway ./services/discord-gateway
 COPY services/discord-gateway/drizzle ./drizzle
 
-# Build
+# Build (combined to reduce layers)
 RUN --mount=type=cache,id=pnpm-store,target=/root/.local/share/pnpm/store \
-    pnpm --filter './packages/shared' run build
-RUN --mount=type=cache,id=pnpm-store,target=/root/.local/share/pnpm/store \
-    pnpm --filter './services/discord-gateway' run build
+    pnpm --filter './packages/shared' run build \
+    && pnpm --filter './services/discord-gateway' run build \
+    && apt-get clean \
+    && rm -rf /var/lib/apt/lists/*
 
 # Create production-only deployment (no devDeps)
 RUN pnpm deploy --legacy --filter '@bete/discord-gateway' /tmp/deploy \