perf: reuse UI build artifact for source map upload in CI

Pass build output from check-ui to upload-sourcemaps via artifact
instead of rebuilding from scratch. Saves ~4-5 min (npm ci + npm run build)
from the upload-sourcemaps job.

.gitea/workflows/release.yaml

@@ -55,6 +55,13 @@ jobs:
       - name: Build
         run: npm run build
 
+      - name: Upload build artifacts
+        uses: actions/upload-artifact@v4
+        with:
+          name: ui-build
+          path: ui/build
+          retention-days: 1
+
   # ── docker: backend ───────────────────────────────────────────────────────────
   docker-backend:
     name: Docker / backend
@@ -140,29 +147,18 @@ jobs:
     name: Upload source maps
     runs-on: ubuntu-latest
     needs: [check-ui]
-    defaults:
-      run:
-        working-directory: ui
     steps:
-      - uses: actions/checkout@v4
-
-      - uses: actions/setup-node@v4
-        with:
-          node-version: "22"
-          cache: npm
-          cache-dependency-path: ui/package-lock.json
-
-      - name: Install dependencies
-        run: npm ci
-
       - name: Compute release version (strip leading v)
         id: ver
         run: |
           V="${{ gitea.ref_name }}"
           echo "version=${V#v}" >> "$GITHUB_OUTPUT"
 
-      - name: Build with source maps
-        run: npm run build
+      - name: Download build artifacts
+        uses: actions/download-artifact@v4
+        with:
+          name: ui-build
+          path: build
 
       - name: Install sentry-cli
         run: npm install -g @sentry/cli