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

backend/src/applications/entities/application.entity.ts

@@ -32,6 +32,12 @@ export class Application {
   @Column({ nullable: true })
   gitUrl: string;
 
+  @Column({ nullable: true })
+  gitToken: string; // Personal access token for private repos
+
+  @Column({ nullable: true })
+  gitBranch: string; // Branch to clone (default: main)
+
   @Column({ nullable: true })
   codePath: string; // Path to uploaded zip