install frontend devDependencies explicitly in the build stage

vite and the build toolchain live under devDependencies; proxied/base-image
npm defaults to omit=dev, leaving 'vite: not found' at build time. Force
--include=dev so the build stage always has its toolchain.

Dockerfile

@@ -45,10 +45,14 @@ COPY frontend/package*.json ./frontend/
 # guard keeps NODE_EXTRA_CA_CERTS unset on a clean checkout (no cert), so Node
 # does not warn about a missing cert path; a proxy-inspected build still gets
 # the cert because the file is present.
+# Force devDependencies in: vite and the rest of the build toolchain live under
+# devDependencies, and some base images / proxied environments default npm to
+# omit=dev, which leaves `vite: not found` at build time. A build stage always
+# needs them, so include them explicitly regardless of the ambient NODE_ENV.
 RUN if [ -f /usr/local/share/ca-certificates/corp-root-ca.crt ]; then \
         export NODE_EXTRA_CA_CERTS=/usr/local/share/ca-certificates/corp-root-ca.crt; \
     fi; \
-    cd frontend && npm ci
+    cd frontend && npm ci --include=dev
 
 # The frontend keeps its repo-relative layout here, because npm prebuild runs
 # `node ../scripts/stage-frontend.mjs`, which stages each plugin's frontend/ into