[Feature Request] Add Registry Provider for Application Deployments

What problem will this feature address?

Currently, Dokploy supports deploying applications from various sources (GitHub, GitLab, Docker Hub, etc.), but there's no convenient way to deploy directly from private Docker registries configured in the system. Users had to manually type the full image path, credentials, and registry URL in the Docker provider form — a cumbersome and error-prone process.

Describe the solution

Enhanced the existing Docker provider tab with a registry browser:

1. Registry selector — Choose from registries already configured in the system
2. Image browser — Searchable combobox that fetches the image catalog from the selected registry via /v2/_catalog
3. Tag browser — Searchable combobox that fetches available tags via /v2/{image}/tags/list
4. Auto-fill — Selecting a tag automatically populates the Docker image path, username, password, and registry URL fields
5. Manual fallback — The original manual input fields remain available when no registry is selected

Why this approach

• No new source type or deployment pipeline needed — reuses the existing Docker deployment workflow
• Credentials and image path are still stored the same way, so existing deployments are unaffected
• Less complexity, same end result: users can deploy from private registries with just a few clicks

Describe alternatives you've considered

1. Manual Docker deployment: Requires SSH access and breaks the Dokploy workflow.
2. Using Docker Hub: Doesn't work for private/enterprise registries.
3. Custom scripts: Bypasses Dokploy's management features.
4. Docker Compose: Requires additional configuration and doesn't integrate with Dokploy's UI.

Additional context

Implemented in #3903.

Will you send a PR to implement it?

Yes — see #3903

Review pull request #3903 first, since the issue says the feature is already implemented there. Start at the existing Docker provider tab and the registry endpoints /v2/_catalog and /v2/{image}/tags/list; verify registry selection, image and tag browsing, credential and image-path auto-fill, and the manual fallback match the requested behavior.