fix: correct package versions and npm flags

Frontend package.json fixes:
- react-router-dom: ^6.31.0 → ^6.30.1 (6.31.0 doesn't exist)
- postcss: ^8.5.1 → ^8.5.6 (use latest stable version)

Setup script fixes:
- Replace deprecated --production flag with --omit=dev
- Resolves npm warning: 'npm WARN config production Use --omit=dev instead'

Fixes npm install errors:
- 'No matching version found for react-router-dom@^6.31.0'
- Deprecated npm configuration warnings

README.md

@@ -68,6 +68,21 @@ For getting started with Docker, see the [Docker documentation](https://github.c
 
 Run on a clean Ubuntu/Debian server with internet access:
 
+#### Debian:
+```bash
+apt update -y
+apt upgrade -y
+apt install curl -y
+```
+
+#### Ubuntu:
+```bash
+apt-get update -y
+apt-get upgrade -y
+apt install curl -y
+```
+
+#### Script
 ```bash
 curl -fsSL -o setup.sh https://raw.githubusercontent.com/9technologygroup/patchmon.net/main/setup.sh && chmod +x setup.sh && bash setup.sh
 ```