feat(templates): add a test, lint, and format setup to every starter

[Bccorb]

A scaffolded project could be built but not verified. Every starter had a lint script and nothing
else, so a user's first move after seamless init was to pick a test runner and wire it up
themselves. This gives all four starters the same working setup on the first npm install.

One command

Every template now declares the same script names, so npm run check is the whole gate:

npm run check   # typecheck && lint && format:check && test

Plus typecheck, lint, lint:fix, format, format:check, test, test:watch, and
test:coverage.

Tests

Vitest, colocated as *.test.ts / *.test.tsx. They cover the configuration and startup logic that
decides whether a fresh scaffold runs at all, and need no database, auth server, or network.

Template	Tests
Express, Fastify	src/lib/databaseUrl.test.ts (which connection string wins, credential escaping, sslmode becoming a driver option), src/lib/env.test.ts (the boot-time check, including the USER and PASSWORD placeholders seamless init writes into a managed DATABASE_URL)
react-vite	src/lib/runtimeConfig.test.ts, src/lib/api.test.ts, src/components/ConfigurationError.test.tsx
react-oauth	the above, plus src/pages/OAuthCallback.test.tsx covering the callback route with the SDK and router stubbed

Web tests are configured in the test block of each vite.config.ts, so they share the app's Vite
resolution and plugins. The API starters need no Vitest config; the defaults already fit.

These are a starting point a user extends, not exhaustive coverage. Anything crossing the network
belongs in an integration or end-to-end test against the real stack.

Lint and format

Prettier now owns formatting, with eslint-config-prettier last in each flat config so the two
cannot disagree about the same line.

ESLint in the API starters now covers the whole project rather than src only, and uses Node
globals instead of browser globals. That surfaced a real finding: an unused catch binding in
scripts/runMigrations.js in both API starters, now fixed.

The API starters build with a tsconfig.build.json that keeps tests out of dist/, while
npm run typecheck still checks them.

CI

The per-template job now runs typecheck, lint, format check, tests, and build. Each step is
--if-present, so a template that has not adopted one is skipped rather than failed, but a declared
script has to pass.

The job renamed from Build <id> to Check <id>. If those names are pinned as required status
checks in branch protection, they need updating.

Note on the diff

Making format:check meaningful took a one-time prettier --write pass. That is most of the diff
outside the new files: quote style in main.tsx, README table alignment, JSX wrapping, indentation
in package.json. It changes no behavior.

Verification

npm run validate passes. npm run check and npm run build pass in all four templates, including
from a clean node_modules.