ci: gitea actions for the suites, the image and the APK

Four workflows, none of which existed:

* `tests.yml` — backend, desktop, `:core` and the web app's typecheck+build, in
  parallel. `:core` needs no Android SDK at all, because settings.gradle.kts
  leaves `:app` out when there is none; `:app`'s Robolectric suite therefore
  lives in the APK workflow, where the SDK is installed anyway. Nothing needs a
  running backend — the suites feed on committed fixtures, which is the whole
  reason they were written that way.
* `lint.yml` — ruff, which the repo had been configured for and never run.
* `docker.yml` — builds the image, *starts* it against SQLite and waits for
  /api/health before pushing, then publishes `:latest` and `:<short-sha>` to
  git.timka.su. A tag nobody can run is worse than no tag.
* `android-release.yml` — the release APK on every push to master, signed from
  secrets, with `apksigner verify --print-certs` reporting which key was really
  used and failing if it was the debug one.

Three things the repo needed before any of that could work:

`versionCode` was pinned at 1, so every APK looked like the same version to the
phone and would not install over its predecessor. It now comes from the run
number, with `versionName` from a property, both via one `setting()` helper that
reads a Gradle property or an environment variable.

The release build fell back to the *debug* signing key whenever the keystore was
missing — silently. That is a trap: the APK installs, looks fine, and can never
be upgraded by a properly signed build. `KADENCE_REQUIRE_SIGNING=1` makes that
case fail the build instead, and the release job sets it whenever a keystore
secret is present.

The compose files built an image with no name, so there was nothing to pull.
`image:` now names the registry tag while `up --build` still builds locally.

Also: `android/ci/install-sdk.sh` (idempotent, cacheable, and the one place that
knows `platforms;android-37.0` is spelled with the minor version), the runner as
a compose service with its config and a setup checklist, six make targets, and a
README section. No runner is registered yet — `make ci-runner` is step two of
that checklist.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

.gitea/workflows/docker.yml

@@ -0,0 +1,70 @@
+# Build the backend + web image and push it to this Gitea's own registry.
+#
+# The image is the same one `docker compose` builds locally — one Dockerfile,
+# two stages, Vite's output baked in and served from the same origin as the API.
+# Tagged twice: `latest` for the deploy script to pull, and the short commit for
+# every build to be nameable after the fact.
+#
+# Needs a runner that can reach a docker daemon. The compose service in
+# `docker-compose.ci.yml` mounts the host's socket into the job container, which
+# is the usual arrangement for a single-machine Gitea.
+name: docker
+
+on:
+  push:
+    branches: [master]
+    tags: ["v*"]
+
+env:
+  REGISTRY: git.timka.su
+  IMAGE: git.timka.su/timka123/kadence
+
+jobs:
+  image:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Check the daemon is reachable
+        run: docker version
+
+      - name: Log in to the Gitea registry
+        run: |
+          echo "${{ secrets.REGISTRY_TOKEN }}" \
+            | docker login "$REGISTRY" -u "${{ secrets.REGISTRY_USER }}" --password-stdin
+
+      - name: Build
+        run: |
+          SHORT="$(git rev-parse --short HEAD)"
+          echo "SHORT=$SHORT" >> "$GITHUB_ENV"
+          docker build -t "$IMAGE:$SHORT" -t "$IMAGE:latest" .
+
+      - name: Smoke-test the image before it is published
+        run: |
+          # A tag nobody can run is worse than no tag. SQLite keeps this to one
+          # container: no database service, no network, no .env.
+          docker run -d --name kadence-smoke \
+            -e DATABASE_URL="sqlite:///./kadence.db" \
+            -e SCHEDULER_ENABLED=0 -e TELEGRAM_BOT_ENABLED=0 \
+            -p 18000:8000 "$IMAGE:$SHORT"
+          for _ in $(seq 1 30); do
+            if curl -fsS http://127.0.0.1:18000/api/health >/dev/null 2>&1; then
+              echo "healthy"; break
+            fi
+            sleep 2
+          done
+          curl -fsS http://127.0.0.1:18000/api/health
+          docker logs kadence-smoke | tail -20
+          docker rm -f kadence-smoke
+
+      - name: Push
+        run: |
+          docker push "$IMAGE:$SHORT"
+          docker push "$IMAGE:latest"
+
+      - name: Push the tag, when there is one
+        if: startsWith(github.ref, 'refs/tags/v')
+        run: |
+          VERSION="${GITHUB_REF#refs/tags/}"
+          docker tag "$IMAGE:$SHORT" "$IMAGE:$VERSION"
+          docker push "$IMAGE:$VERSION"