feat: self-hosted GitLab Apps OAuth integration

Adds self-hosted GitLab OAuth sources so Coolify can connect to a self-managed GitLab instance, list private repositories, clone over an OAuth token, and deploy (the GitLab counterpart to GitHub Apps).

Hardening: authenticated, one-time team-bound OAuth callback state; token redaction in deploy logs; custom host port/path kept in clone and ls-remote URLs; submodule OAuth auth; system-wide source selection. Covered by unit and feature tests.

cosigned by OpenAI Codex at M1 Max

app/Providers/AppServiceProvider.php

@@ -102,5 +102,16 @@ class AppServiceProvider extends ServiceProvider
                 ])->baseUrl($api_url);
             }
         });
+
+        Http::macro('GitLab', function (string $api_url, ?string $access_token = null) {
+            $client = Http::withHeaders([
+                'Accept' => 'application/json',
+            ])->baseUrl($api_url);
+            if ($access_token) {
+                $client = $client->withToken($access_token);
+            }
+
+            return $client;
+        });
     }
 }