perf(admin-panel): cache the Nx build sub-targets

[fxa-agent]

Because

• Commit 9625ff7 (the Nx upgrade) moved build-css, build-react, build-ts-client and build-ts-server into dependsOn of build, with no cache settings.
• Nx therefore runs all four on every build. This happens in the CI Build job and in start-services.sh on each Playwright node.

This pull request

• Adds cache: true, inputs and outputs to the four sub-targets in the nx.targets block of packages/fxa-admin-panel/package.json. build-css is a new entry.

Issue that this pull request solves

Closes: FXA-14727

Checklist

Put an x in the boxes that apply

• My commit is GPG signed.
• If applicable, I have modified or added tests which pass locally.
• I have added necessary documentation (if appropriate).
• I have verified that my changes render correctly in RTL (if appropriate).
• I have manually reviewed all AI generated code.

How to review (Optional)

• Key files/areas to focus on: the nx.targets block of packages/fxa-admin-panel/package.json. The scripts block and nx.json are unchanged.
• Suggested review order: build-css, build-react, then the two build-ts-* targets.
• Risky or complex parts: the outputs. build/ is not declared as a whole, because webpack cleans build/ but keeps libs/ and packages/ (the server tsc output). build-react declares index.html, favicon.ico and static. build-css and build-react use NODE_ENV as an input, because tailwind.config.js branches on it.
• One reviewer call: two limits of the prescribed inputs are kept as they are. (a) The production input excludes test and story files. A change to only those files is a cache hit on build-ts-client and skips its type check. (b) build-react lists the two public/ files by name. A new file in public/ must also be added to its outputs. Do you accept both?

Screenshots (Optional)

Other information (Optional)

This change has no test files. This is what I ran in the VM with /fxa-verify --plan. All checks passed.

• nx show project fxa-admin-panel --json shows cache: true and the inputs and outputs above on all four targets.
• A second NODE_ENV=test nx run fxa-admin-panel:build took all four sub-targets from cache (15 s).
• After rm -rf build src/styles/tailwind.out.css, a cached build restored build/index.html, build/favicon.ico, build/static, build/libs, build/packages and tailwind.out.css (16 s).
• Byte compare: I took the sha256 of every file under build/ plus tailwind.out.css. I compared a cache-restored build with a fresh --skip-nx-cache run of each sub-target. Both lists have 65 files and are identical. For example build/index.html starts with 16f8fc1c7099 and build/favicon.ico with 05f3b705513a.
• NODE_ENV from test to development, with a fresh isolated Nx cache: build-css and build-react ran. build-ts-client and build-ts-server came from cache.
• Serve check: the admin-panel server on port 8091 with no PROXY_STATIC_RESOURCES_FROM. Output: GET / 200, index.html assets match build/, GET /static/css/main.1cfb0b2e.css 200, GET /static/js/main.cad72f5a.js 200.
• packages/functional-tests/tests/admin/adminPanel.spec.ts against that server: 3 passed ("admin panel loads and renders navigation", "admin panel heartbeat is healthy", "admin server heartbeat is healthy").

Not run in the VM, left to CI:

• The two account search tests in adminPanel.spec.ts. In the VM the API test got 500 because the admin server cannot reach Stripe. The UI test got 403 because a production bundle sends no test-user headers (getExtraHeaders in src/lib/config.ts sends them only when NODE_ENV is development). The byte compare shows the cache does not change the bundle.
• The CI Build and start-services timings. The baseline is CI job 714508: 81 s for the Build step and 38 s for the start-services build. The CI run of this PR gives the new numbers.

admin-adminPanel-Admin-Pan-8aff4-oads-and-renders-navigation-local.webm

[Copilot]

🟡 Changes recommended

Moderate cache correctness issues remain unresolved.

1 open finding

• Production inputs omit test files checked by build-ts-client · New

What changed in this PR

Adds Nx caching for the admin-panel CSS, React, and TypeScript build targets to reduce repeated CI and Playwright builds.

Changes:

• Configures caching inputs and outputs for four build sub-targets.
• Tracks generated CSS, React assets, and TypeScript outputs.
• Adds the CSS dependency to the React build target.

File	Summary
packages/​fxa-admin-panel/​package.json	Adds caching configuration. Findings: two moderate issues regarding TypeScript test/story inputs and incomplete public/ outputs, plus one nit regarding redundant NODE_ENV input.

🧠 Review effort: Lite

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[vbudhram]

Improvement that only impacts admin panel