fix: make source maps opt-in to restore v1.67.0 memory baseline

Production source maps (--enable-source-maps) caused a ~50% memory increase
(600MB to 1000MB) in v1.68.0. Node.js loads all .map files into memory when
this flag is enabled, and Next.js server chunks generate hundreds of map files.

Changes:
- Guard productionBrowserSourceMaps and serverSourceMaps behind
  HOMARR_ENABLE_SOURCE_MAPS env var (default off)
- Guard .map copy step and NODE_OPTIONS in Dockerfile behind
  ENABLE_SOURCE_MAPS build arg (default false)
- run.sh checks HOMARR_ENABLE_SOURCE_MAPS before setting --enable-source-maps
- Add Docker-based memory regression CI job (<700MB threshold)

Closes #6123

.github/workflows/code-quality.yml

@@ -163,3 +163,58 @@ jobs:
         run: cp .env.example .env
       - name: Build
         run: pnpm turbo build --affected
+
+  memory-regression:
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+    steps:
+      - uses: actions/checkout@v6
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v4
+      - name: Build Docker image
+        uses: docker/build-push-action@v7
+        with:
+          platforms: linux/amd64
+          context: .
+          push: false
+          load: true
+          tags: homarr-memory-test
+          network: host
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
+        env:
+          SKIP_ENV_VALIDATION: true
+      - name: Start container and measure memory
+        run: |
+          docker run -d --name homarr-mem-test -p 17575:7575 homarr-memory-test
+          # Wait for container to be healthy (up to 60s)
+          for i in $(seq 1 30); do
+            if curl -sf http://localhost:17575/api/health 2>/dev/null; then
+              echo "Container healthy after $((i * 2))s"
+              break
+            fi
+            sleep 2
+          done
+          # Warm up: hit the dashboard page a few times
+          for i in $(seq 1 5); do
+            curl -sf http://localhost:17575/ > /dev/null 2>&1 || true
+            sleep 2
+          done
+          # Measure RSS after warmup
+          MEM_KB=$(docker stats --no-stream --format '{{.MemUsage}}' homarr-mem-test | sed 's| /.*||')
+          echo "Raw memory: $MEM_KB"
+          # Convert to numeric MB (handles GiB and MiB suffixes)
+          MEM_NUM=$(echo "$MEM_KB" | awk '{
+            if ($0 ~ /GiB/) { gsub(/GiB/,""); print $1 * 1024 }
+            else if ($0 ~ /MiB/) { gsub(/MiB/,""); print $1 }
+            else if ($0 ~ /KiB/) { gsub(/KiB/,""); print $1 / 1024 }
+            else { print $1 / 1048576 }
+          }')
+          echo "Memory usage: ${MEM_NUM} MB"
+          MAX_MB=700
+          if awk "BEGIN {exit !($MEM_NUM > $MAX_MB)}"; then
+            echo "ERROR: Memory usage ${MEM_NUM} MB exceeds ${MAX_MB} MB threshold"
+            docker logs homarr-mem-test --tail 50
+            exit 1
+          fi
+          echo "Memory check passed: ${MEM_NUM} MB <= ${MAX_MB} MB"