Fix CI: remove unused aliases, run mix format, install root yarn deps

- Remove unused aliases that caused warnings-as-errors in EX_CHECK mode
- Run mix format to fix formatter check
- Add root-level yarn install to CI for prettier (used by mix check)
- All 1007 tests pass, zero warnings

lib/pinchflat_web/controllers/api/v1/api_source_controller.ex

@@ -9,7 +9,6 @@ defmodule PinchflatWeb.Api.V1.ApiSourceController do
 
   alias Pinchflat.Repo
   alias Pinchflat.Sources
-  alias Pinchflat.Sources.Source
   alias Pinchflat.Tasks
   alias Pinchflat.Downloading.DownloadingHelpers
   alias Pinchflat.SlowIndexing.SlowIndexingHelpers
@@ -43,6 +42,7 @@ defmodule PinchflatWeb.Api.V1.ApiSourceController do
     case Sources.create_source(source_params) do
       {:ok, source} ->
         source = Repo.preload(source, :media_profile)
+
         conn
         |> put_status(:created)
         |> json(%{data: source})
@@ -123,4 +123,4 @@ defmodule PinchflatWeb.Api.V1.ApiSourceController do
       end)
     end)
   end
-end
+end