Add usage_caps_input slot to the project settings page

[elias-ba]

Add a usage_caps_input view-extension slot to the project settings page. Same pattern as the existing concurrency_input slot.

What's being added

In LightningWeb.ProjectLive.Settings.apply_action(:edit, ...), read the component from route metadata next to the existing concurrency_input_component lookup:

usage_caps_input_component =
  socket.router
  |> Phoenix.Router.route_info("GET", ~p"/projects/:project_id/settings", nil)
  |> Map.get(:usage_caps_input)

Assign it to usage_caps_input_component and render it from settings.html.heex:

<.live_component
  :if={assigns[:usage_caps_input_component]}
  module={assigns[:usage_caps_input_component]}
  id="usage-caps-input"
  project={@project}
  current_user={@current_user}
/>

Downstream apps populate the slot by attaching metadata: %{usage_caps_input: SomeComponent} to the settings route. The component receives project and current_user.

Acceptance criteria

1. /projects/:project_id/settings reads :usage_caps_input from its route metadata and exposes it as @usage_caps_input_component.
2. The template renders the component when set, nothing when not.
3. The component receives project and current_user.
4. No new UI in OSS Lightning by default.
5. concurrency_input keeps working unchanged.