build: ship pre-built API bundle; images copy output instead of installing

- API: `pnpm build` bundles dist/ into apps/api/.output (esbuild), with
  Linux musl native packages for sharp and argon2 kept alongside
- docker/api.Dockerfile copies that output; no pnpm install on the server
- add dist/migrate.js (prisma migrate deploy equivalent, same
  _prisma_migrations table and lock) so the Prisma CLI is not needed at runtime
- pnpm-workspace: supportedArchitectures for linux/x64/musl
- admin: apps/admin/.env.production sets VITE_SITE_URL for the production build
- drop NPM_REGISTRY / SITE_URL build args from compose and .env.example
- gitignore: anchor node_modules rules so pre-built node_modules are committed
- README: describe the pre-built deploy flow

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>

apps/api/.output/node_modules/@node-rs/argon2/browser.js

@@ -0,0 +1 @@
+export * from '@node-rs/argon2-wasm32-wasi'