CI: cache Android SDK/NDK, Gradle, and npm across APK builds

Persist three Docker volumes into the build job (android-sdk, gradle home, npm
cache) and enable the Gradle build cache, so repeat builds skip the ~2GB NDK
download, Maven dependency resolution, and unchanged native/Kotlin compilation
— cutting builds from ~1h to a few minutes after the first run.

The runner must whitelist these volumes via config.yaml (container.valid_volumes);
deploy-runner.sh now writes that config, pre-creates the volumes, and starts the
daemon with --config. Requires re-running deploy-runner.sh on the runner host
before the next tag.

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

scripts/deploy-runner.sh

@@ -61,6 +61,24 @@ mkdir -p "$INSTALL_DIR/data"
 # The runner image runs as uid/gid 1000 and must own its config dir.
 chown -R 1000:1000 "$INSTALL_DIR/data"
 
+# Runner config: allow the build workflow to mount the persistent cache volumes
+# (Android SDK/NDK, Gradle home, npm cache) so APK builds don't redownload and
+# recompile everything each run. Without valid_volumes listed, the runner
+# rejects the workflow's `volumes:` and the job fails.
+cat > "$INSTALL_DIR/config.yaml" <<'CONFIG'
+container:
+  valid_volumes:
+    - camptickets-android-sdk
+    - camptickets-gradle
+    - camptickets-npm
+CONFIG
+chown 1000:1000 "$INSTALL_DIR/config.yaml"
+
+# Pre-create the named cache volumes (idempotent).
+docker volume create camptickets-android-sdk >/dev/null
+docker volume create camptickets-gradle >/dev/null
+docker volume create camptickets-npm >/dev/null
+
 cat > "$INSTALL_DIR/docker-compose.yml" <<COMPOSE
 services:
   runner:
@@ -72,6 +90,7 @@ services:
       - "\${DOCKER_GID}"
     volumes:
       - ./data:/data
+      - ./config.yaml:/data/config.yaml:ro
       - /var/run/docker.sock:/var/run/docker.sock
     env_file: .env
     command:
@@ -86,7 +105,7 @@ services:
             --name "\${RUNNER_NAME}" \\
             --labels "${JOB_LABEL}"
         fi
-        exec forgejo-runner daemon
+        exec forgejo-runner daemon --config /data/config.yaml
 COMPOSE
 
 # Preserve an existing token line if re-running without a new token.