fix: revert npm ci to npm install --include=dev in [build] command

npm ci failed in Cloudflare Workers Builds CI — the same failure was
encountered and fixed in commit 629dbf7. Their build environment
appears to omit devDependencies during npm ci, which causes the
react-scripts build to fail (react-scripts is a devDep).
npm install --include=dev explicitly forces devDep installation and
was the confirmed-working form.

https://claude.ai/code/session_013cFiQZ1hnb4JrBj9DvDgip

Author: claude

wrangler.toml

@@ -9,7 +9,7 @@ compatibility_flags = ["nodejs_compat"]
 # Installs frontend deps and builds the SPA so frontend/build exists before
 # `wrangler deploy` uploads assets.  NODE_OPTIONS is required for
 # react-scripts 5.x + Node 18+ (webpack 4 OpenSSL 3.0 compatibility).
-command = "cd frontend && npm ci && GENERATE_SOURCEMAP=false CI=false NODE_OPTIONS=--openssl-legacy-provider npm run build"
+command = "cd frontend && npm install --include=dev && GENERATE_SOURCEMAP=false CI=false NODE_OPTIONS=--openssl-legacy-provider npm run build"
 
 # ─── Static Assets (React SPA build output) ──────────────────────────────────
 # Built by `npm run build` (root package.json) before every `wrangler deploy`.