docs: document self-hosted GitLab / GitLab Enterprise support

platform/repositories/gitlab.mdx

@@ -1,6 +1,6 @@
 ---
 title: "GitLab"
-description: "Configure repository access for GitLab.com."
+description: "Configure repository access for GitLab.com and self-hosted GitLab."
 ---
 
 ## Prerequisites
@@ -72,3 +72,25 @@ This is required to create a service account for Hacktron to use.
 </Steps>
 
 That's it! Hacktron will now run security reviews for every pull request in the selected repositories.
+
+## Self-hosted GitLab / GitLab Enterprise
+
+Hacktron supports self-hosted GitLab and GitLab Enterprise through the same
+Personal Access Token flow described above. The only difference is one extra
+step when you connect.
+
+Follow the same **Configure access** steps to create a service account
+(**Settings** → **Service Accounts**), grant it Maintainer access, and generate
+a token from the service account's **Manage access tokens** with the `api`,
+`read_api`, and `read_user` scopes. These are identical to GitLab.com.
+
+When you open the **Connect GitLab** modal in Hacktron, select **Self-hosted /
+GitLab Enterprise** and enter your instance's base URL (e.g.
+`https://gitlab.example.com`) before entering the token.
+
+<Note>
+  Self-hosted prerequisites:
+  - Your GitLab instance must be network-reachable from Hacktron.
+  - The service account's token must carry the `api`, `read_api`, and
+    `read_user` scopes on your self-hosted instance.
+</Note>