UI to Select Dataclips on Sandbox Creation

We need to add a dataclip selection interface to the sandbox creation modal, allowing users to choose which named dataclips from the parent project should be copied to the new sandbox.

Currently, when creating a sandbox via Lightning.Projects.Sandboxes.provision/3, no dataclips are copied by default. The backend supports selective dataclip copying through the dataclip_ids parameter, but there's no UI to expose this functionality.

The backend already supports dataclip selection:

• The provision_attrs includes optional dataclip_ids parameter
• copy_selected_dataclips/3 handles filtering and copying
• Only allows copying of named dataclips with types: :global, :saved_input, :http_request
• Generates new UUIDs for copied dataclips in the sandbox

Consider updating the LightningWeb.SandboxLive.FormComponent to:

• Add dataclip selection state management
• Fetch parent project's eligible dataclips on component mount
• Handle empty state when no dataclips are available

Consider adding a new dataclip picker component based on existing multi-select patterns in the app. The new dataclip picker component should be implemented in LightningWeb.SandboxLive.Components and used in the LightningWeb.SandboxLive.FormComponent.

Define it like this in the Components module:

def dataclip_picker(assigns) do
  # Checkbox list of available named dataclips
  # Show dataclip names, types, creation dates
  # Group by type (Global, Saved Input, HTTP Request)
  # Include search/filter functionality for large lists
  # Show "No dataclips available" empty state
end

Use it like this in the FormComponent module:

<Components.dataclip_picker 
  id="dataclip-selection"
  dataclips={@eligible_dataclips}
  selected={@selected_dataclips}
  loading={@loading_dataclips}
  on_change={...}
/>

The user experience flow should look like this:

1. User clicks "Create Sandbox"
2. Modal opens with basic fields (name, env, color)
3. Dataclip section shows at bottom with loading state
4. Available dataclips load asynchronously, grouped by type
5. User can expand/collapse type groups and select individual dataclips
6. Search helps users find specific dataclips by name
7. Form submission includes selected dataclip IDs
8. Backend copies selected dataclips to new sandbox

Few recommendations:

• Leveraging existing @allowed_dataclip_types constant from backend
• Using async pattern similar to other data loading in Lightning
• Implementing virtual scrolling or pagination when there are too many dataclips to load
• Handling errors when fetching dataclips
• Respecting user permissions for viewing parent dataclips
• Considering debouncing search input
• Ensuring proper cleanup of selected dataclips when component unmounts

PS: Should we add the possibility for users to flag dataclips as eligible to be copied in Sanboxes ? For now only named dataclips are elligible to be copied in Sandboxes. cc @josephjclark

Start with LightningWeb.SandboxLive.FormComponent and the LightningWeb.SandboxLive.Components module, then trace Lightning.Projects.Sandboxes.provision/3 and the existing copy_selected_dataclips/3 behavior. Done means the sandbox modal loads eligible named dataclips, supports grouped selection and filtering with an empty state, and submits selected dataclip IDs for copying.