Change Channel to Source (#12)

* Ensure channel detail lookup doesn't download the video - oops

* Ran the needful migrations for replacing channels with sources

* got media source test back working

* channel tasks test

* Media indexing worker test

* media tests

* Got all tests working except controller tests

* got all tests working

* Renamed Channel struct to Source

* renamed ChannelTasks

* More renaming; renamed channel details module

* Removed Channel yt-dlp module, instead throwing things in the VideoCollection module

* Renamed what looks like the last of the outstanding data

lib/pinchflat_web/controllers/media_sources/source_html/new.html.heex

@@ -0,0 +1,12 @@
+<.header>
+  New Source
+  <:subtitle>Use this form to manage source records in your database.</:subtitle>
+</.header>
+
+<.source_form
+  changeset={@changeset}
+  media_profiles={@media_profiles}
+  action={~p"/media_sources/sources"}
+/>
+
+<.back navigate={~p"/media_sources/sources"}>Back to sources</.back>