docs: note disabling Apache before nginx install

We hit this exact conflict during setup (Apache pre-installed and
bound to port 80), so nginx failed to start until it was disabled.

README.md

@@ -217,6 +217,12 @@ sudo apt install -y nginx
 nginx -v
 ```
 
+> If Apache is already installed, it will also be bound to port 80/443 and nginx will fail to
+> start. Disable it first:
+> ```sh
+> sudo systemctl disable --now apache2
+> ```
+
 The repo includes `nginx.conf` in the project root. Install it as the active site config:
 
 ```sh
@@ -546,7 +552,10 @@ sudo apt install -y nginx
 ```
 
 > If another web server (e.g. Apache) is already bound to port 80/443, nginx will fail to start.
-> Check with `sudo ss -tlnp | grep -E ':80|:443'` and disable the conflicting service first.
+> Check with `sudo ss -tlnp | grep -E ':80|:443'` and disable the conflicting service first:
+> ```sh
+> sudo systemctl disable --now apache2
+> ```
 
 ### Step 3 — Install certbot with the Cloudflare DNS plugin