Add dev/production update channels, clearer Euchre table, bolder Sequence highlight

Update channels
- ci.yml now publishes each green push to dev as a prerelease tagged
  v1.0.<n>-dev, so the dev channel has something to install. Workflow
  artifacts could not serve this: downloading one needs authentication,
  which the app does not have.
- Prereleases specifically, because GitHub's "latest release" endpoint
  skips them — a production install can never be handed a dev build.
  Pull requests build and check but never publish.
- Settings gains a channel picker. The two channels are numbered by
  separate workflow run counters, so versions are only compared within a
  channel; the app reads the -dev suffix in its own versionName to know
  where it stands, and treats a channel change as an explicit switch. The
  screen warns that such a switch can be a downgrade Android will refuse.
- PLG_RELEASE becomes PLG_CHANNEL, naming the channel rather than a flag.

Euchre
- Cards in a trick now sit on the side of the table belonging to whoever
  played them, rotated to face them, labelled You / Left / Partner /
  Right. Previously they were a flat row tagged with seat numbers, which
  made it hard to tell who had played what.
- Bidding says what it will actually do. As dealer the button reads "Pick
  it up" rather than "Order up", since the turn card comes to your hand,
  and a line of explanatory text spells out the consequence either way.

Sequence
- Playable squares get a much heavier outline, scaled off cell size and
  in a fixed amber that reads against a white card, a green corner and a
  chip alike. The old 2dp theme-coloured border was hard to see.

Co-Authored-By: Claude Opus 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_015qjfMiPUDshdKEUa6vxqzN

.github/workflows/release.yml

@@ -25,10 +25,9 @@ jobs:
     if: github.ref == 'refs/heads/main'
     runs-on: ubuntu-latest
     env:
-      # Tells the build this is a real release, so the APK is stamped with the
-      # run number that matches the tag below. Absent everywhere else, which
-      # keeps dev and local builds at 1.0.0-dev.
-      PLG_RELEASE: "1"
+      # Stamps the APK as a production-channel build, versioned with the run
+      # number that matches the tag published below.
+      PLG_CHANNEL: production
     steps:
       - name: Checkout
         uses: actions/checkout@v4