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/@img/sharp-libvips-linuxmusl-x64/package.json

@@ -0,0 +1,43 @@
+{
+  "name": "@img/sharp-libvips-linuxmusl-x64",
+  "version": "1.3.4",
+  "description": "Prebuilt libvips and dependencies for use with sharp on Linux (musl) x64",
+  "author": "Lovell Fuller <npm@lovell.info>",
+  "homepage": "https://sharp.pixelplumbing.com",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/lovell/sharp-libvips.git",
+    "directory": "npm/linuxmusl-x64"
+  },
+  "license": "LGPL-3.0-or-later",
+  "funding": {
+    "url": "https://opencollective.com/libvips"
+  },
+  "preferUnplugged": true,
+  "publishConfig": {
+    "access": "public"
+  },
+  "files": [
+    "lib",
+    "versions.json"
+  ],
+  "type": "commonjs",
+  "exports": {
+    "./lib": "./lib/index.js",
+    "./package": "./package.json",
+    "./versions": "./versions.json",
+    "./binary": "./lib/libvips-cpp.so.8.18.7"
+  },
+  "config": {
+    "musl": ">=1.2.5"
+  },
+  "os": [
+    "linux"
+  ],
+  "libc": [
+    "musl"
+  ],
+  "cpu": [
+    "x64"
+  ]
+}