feat: support private git repositories with token auth

- Entity: added gitToken and gitBranch columns to Application
- DTO: added gitToken and gitBranch fields to Create/Update DTOs
- Build pipeline: git-clone init container now injects token into
  HTTPS URL for private repo authentication (GitHub PAT, GitLab token, etc.)
- Build pipeline: supports cloning specific branch (default: main)
- Frontend deploy page: added Access Token (password field) and Branch
  inputs when Git Repository source is selected
- Frontend deploy page: Review step shows branch and token status
- Frontend app detail: shows branch badge and 🔑 Private indicator
  when git credentials are configured
- Works with: GitHub, GitLab, Bitbucket, any HTTPS-based git host

frontend/src/app/dashboard/apps/[id]/page.tsx

@@ -453,6 +453,18 @@ export default function AppDetailPage() {
               <div>
                 <p className="text-sm font-medium text-blue-800">Git repository connected</p>
                 <p className="text-xs text-blue-600 font-mono">{app.gitUrl}</p>
+                <div className="flex items-center space-x-3 mt-1">
+                  {app.gitBranch && (
+                    <span className="text-xs text-blue-500">
+                      🌿 {app.gitBranch}
+                    </span>
+                  )}
+                  {app.gitToken && (
+                    <span className="text-xs text-green-600">
+                      🔑 Private
+                    </span>
+                  )}
+                </div>
               </div>
             </div>
           </div>