perf(deploy): parallel deploys, preserve build cache, prod-only runtime deps

Three changes to cut deploy time:
1. deploy.sh: Pi and VM deploy concurrently (wall time = max, not sum)
2. deploy.sh: Build cache capped at 2GB instead of nuked after 24h,
   so pnpm install layer is reused between deploys
3. Dockerfile: runtime stage uses --prod (skip devDeps). Moved tsx
   from devDependencies to dependencies since it's used in CMD.

packages/server/package.json

@@ -26,7 +26,8 @@
     "fastify": "^4.28.1",
     "jsonwebtoken": "^9.0.2",
     "livekit-server-sdk": "^2.6.1",
-    "sharp": "^0.33.0"
+    "sharp": "^0.33.0",
+    "tsx": "^4.16.0"
   },
   "devDependencies": {
     "@types/bcryptjs": "^2.4.6",
@@ -35,7 +36,6 @@
     "@types/node": "^20.14.0",
     "@types/ws": "^8.18.1",
     "drizzle-kit": "^0.24.0",
-    "tsx": "^4.16.0",
     "typescript": "^5.4.0",
     "vitest": "^4.0.18"
   }