fix: source maps — ship pre-built artifact with injected debug IDs to Docker

The docker-ui job was rebuilding the UI from scratch inside Docker, producing
chunk hashes and JS files that didn't match the source maps uploaded to
GlitchTip, causing all stack traces to appear minified.

Fix:
- ui/Dockerfile: add PREBUILT=1 ARG; skip npm run build when set
- release.yaml upload-sourcemaps: re-upload artifact after sentry-cli inject
- release.yaml docker-ui: download injected artifact into ui/build/ and pass
  PREBUILT=1 so Docker reuses the exact same JS files whose debug IDs are in
  GlitchTip

.gitea/workflows/release.yaml

@@ -171,6 +171,13 @@ jobs:
           SENTRY_ORG: libnovel
           SENTRY_PROJECT: ui
 
+      - name: Upload injected build (for docker-ui)
+        uses: actions/upload-artifact@v3
+        with:
+          name: ui-build-injected
+          path: build
+          retention-days: 1
+
       - name: Create GlitchTip release
         run: sentry-cli releases new ${{ steps.ver.outputs.version }}
         env:
@@ -226,6 +233,12 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
+      - name: Download injected build (debug IDs already embedded)
+        uses: actions/download-artifact@v3
+        with:
+          name: ui-build-injected
+          path: ui/build
+
       - uses: docker/setup-buildx-action@v3
 
       - name: Log in to Docker Hub
@@ -255,6 +268,7 @@ jobs:
             BUILD_VERSION=${{ steps.meta.outputs.version }}
             BUILD_COMMIT=${{ gitea.sha }}
             BUILD_TIME=${{ gitea.event.head_commit.timestamp }}
+            PREBUILT=1
           cache-from: type=registry,ref=${{ secrets.DOCKER_USER }}/libnovel-ui:latest
           cache-to: type=inline