CI: dedicated cached runner for this repo (deploy script + volume caches)

- scripts/deploy-runner.sh: compose-managed BigBrainParking Forgejo runner
  (adapted from the Camp Scan one), with valid_volumes for bigbrainparking-gradle
  and bigbrainparking-npm. No android-sdk volume — the RN build image ships it.
- Workflow mounts those caches (GRADLE_USER_HOME + npm cache) and enables the
  Gradle build cache (org.gradle.caching + --build-cache), so repeat builds skip
  the dep re-download and recompile that dominate a cold ~35 min build.

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

.forgejo/workflows/build-apk.yml

@@ -26,6 +26,15 @@ jobs:
       # and NO container swap (--memory-swap == --memory) so it OOM-fails cleanly
       # instead of thrashing the disk with swap. With the JVM caps below it uses ~5 GB.
       options: --cpus=2 --memory=8g --memory-swap=8g
+      # Persistent caches (whitelisted in the runner's config.yaml valid_volumes).
+      # Gradle home = downloaded Maven deps + build cache; npm = package cache.
+      # Repeat builds skip the re-download/re-compile that dominate a cold build.
+      volumes:
+        - bigbrainparking-gradle:/opt/cache/gradle
+        - bigbrainparking-npm:/opt/cache/npm
+    env:
+      GRADLE_USER_HOME: /opt/cache/gradle
+      npm_config_cache: /opt/cache/npm
     steps:
       - uses: actions/checkout@v4
 
@@ -60,6 +69,7 @@ jobs:
           org.gradle.workers.max=2
           org.gradle.parallel=false
           org.gradle.daemon=false
+          org.gradle.caching=true
           kotlin.daemon.jvmargs=-Xmx1536m
           PROPS
 
@@ -73,10 +83,11 @@ jobs:
           # Also cap the no-daemon launcher JVM (org.gradle.jvmargs targets the daemon).
           GRADLE_OPTS: "-Xmx1536m -Djava.net.preferIPv4Stack=true"
         # --max-workers=2 limits concurrent tasks; container --cpus=2 caps clang -j.
+        # --build-cache reuses task outputs from GRADLE_USER_HOME across runs.
         run: >-
           ./gradlew :app:assembleRelease
           -PreactNativeArchitectures=arm64-v8a
-          --no-daemon --max-workers=2
+          --no-daemon --max-workers=2 --build-cache
 
       # Self-contained publish via the Forgejo API (no external action to fetch).
       - name: Publish release + upload APK