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/sharp/dist/index.mjs

@@ -0,0 +1,25 @@
+/*!
+  Copyright 2013 Lovell Fuller and others.
+  SPDX-License-Identifier: Apache-2.0
+*/
+
+import Sharp from './constructor.mjs';
+import input from './input.mjs';
+import resize from './resize.mjs';
+import composite from './composite.mjs';
+import operation from './operation.mjs';
+import colour from './colour.mjs';
+import channel from './channel.mjs';
+import output from './output.mjs';
+import utility from './utility.mjs';
+
+input(Sharp);
+resize(Sharp);
+composite(Sharp);
+operation(Sharp);
+colour(Sharp);
+channel(Sharp);
+output(Sharp);
+utility(Sharp);
+
+export default Sharp;