v0.2: All videos folder, shared watched state, release-order sorting, official icon, OAuth plumbing, docs

- per-creator "All videos" folder (release order across sub-channels); sub-channel copies use
  cpost: ids and UserDataMirror keeps played/resume state in sync
- SortNameUpdater forces release-order sort names so every client lists newest first by default
- official Floatplane icon as channel image (Primary only — a channel Thumb hid video thumbnails
  in Continue Watching) and as 16:9 plugin thumbnail; one-time image replacement on upgrade
- OAuth device-flow login (FloatplaneAuthService + settings UI); needs a Floatplane client id;
  Turnstile verified domain-bound so password login inside Jellyfin is impossible
- generic install.sh (linuxserver / official image / native), thumb.png in package + manifest
- README rewritten for a general audience, doc/usage.md with screenshots, 60 tests

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

build.yaml

@@ -15,4 +15,6 @@ owner: "brasse"
 artifacts:
 - "Jellyfin.Plugin.Floatplane.dll"
 changelog: >
-  Initial release: channel browsing, HLS playback proxy, cookie session, search test.
+  "All videos" folder per creator (release order across sub-channels) with shared
+  watched state, official Floatplane icon, OAuth device-flow login (needs a client id),
+  generic install script, documentation with screenshots.