fix: set npm registry before installing frontend dependencies

Dockerfile

@@ -25,7 +25,8 @@ RUN corepack enable && corepack prepare pnpm@latest --activate
 
 # Install dependencies first (better caching)
 COPY frontend/package.json frontend/pnpm-lock.yaml ./
-RUN pnpm install --frozen-lockfile
+RUN pnpm config set registry https://registry.npmmirror.com/ && \
+    pnpm install --frozen-lockfile
 
 # Copy frontend source and build
 COPY frontend/ ./