Fix prod docker build: native modules and frontend devDeps

Per-package onlyBuiltDependencies so pnpm 10 actually compiles native
modules (isolated-vm, argon2, sqlite3, sharp) — root workspace config
isn't visible when compose mounts a single package into /app.

Frontend container now installs with devDeps (so tsc/vite exist),
prunes after build, and gains a `start` script that serves the build
via vite preview on 0.0.0.0:3000.

Drop obsolete compose `version` key.

frontend/package.json

@@ -12,6 +12,7 @@
     "dev": "vite",
     "build": "tsc -b && vite build",
     "preview": "vite preview",
+    "start": "vite preview --host 0.0.0.0 --port 3000",
     "typecheck": "tsc -b --noEmit",
     "format": "prettier --ignore-unknown --write .",
     "format:check": "prettier --check ."
@@ -46,5 +47,10 @@
     "tailwindcss": "4.2.4",
     "typescript": "6.0.3",
     "vite": "8.0.10"
+  },
+  "pnpm": {
+    "onlyBuiltDependencies": [
+      "esbuild"
+    ]
   }
 }