fix: include PostCSS config in web image

deploy/railway-web.Dockerfile

@@ -6,7 +6,7 @@ RUN npm ci
 
 COPY frontend/src ./src
 COPY frontend/public ./public
-COPY frontend/next.config.ts frontend/tsconfig.json ./
+COPY frontend/next.config.ts frontend/postcss.config.mjs frontend/tsconfig.json ./
 
 ARG NEXT_PUBLIC_SUPABASE_URL
 ARG NEXT_PUBLIC_SUPABASE_ANON_KEY

tests/test_railway_deployment.py

@@ -15,3 +15,11 @@ def test_railway_services_use_the_product_frontend_and_dynamic_ports() -> None:
     assert "COPY SKILL.md mcp_server.py" in api
     assert "--host 0.0.0.0" in api and "${PORT:-5200}" in api
     assert "http.server" not in api
+
+
+def test_web_image_copies_postcss_config_before_building_frontend() -> None:
+    web = (ROOT / "deploy" / "railway-web.Dockerfile").read_text(encoding="utf-8")
+    config_copy = "COPY frontend/next.config.ts frontend/postcss.config.mjs frontend/tsconfig.json ./"
+
+    assert config_copy in web
+    assert web.index(config_copy) < web.index("RUN npm run build")