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/versions.json

@@ -0,0 +1,30 @@
+{
+  "aom": "3.15.1",
+  "archive": "3.8.9",
+  "cairo": "1.18.6",
+  "cgif": "0.5.4",
+  "exif": "0.6.26",
+  "expat": "2.8.5",
+  "ffi": "3.8.0",
+  "fontconfig": "2.18.3",
+  "freetype": "2.14.3",
+  "fribidi": "1.0.17",
+  "glib": "2.90.0",
+  "harfbuzz": "14.5.0",
+  "heif": "1.23.5",
+  "highway": "1.4.0",
+  "imagequant": "2.4.1",
+  "lcms": "2.19.1",
+  "mozjpeg": "0826579",
+  "pango": "1.58.2",
+  "pixman": "0.46.4",
+  "png": "1.6.58",
+  "proxy-libintl": "0.5",
+  "rsvg": "2.63.2",
+  "tiff": "4.7.2",
+  "uhdr": "2.0.2",
+  "vips": "8.18.7",
+  "webp": "1.6.0",
+  "xml2": "2.15.4",
+  "zlib-ng": "2.3.3"
+}