CI: APK only on app changes, Gradle cached

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.github/workflows/release-apk.yml

@@ -3,6 +3,14 @@ name: release-apk
 on:
   push:
     branches: [main]
+    # A publisher, not a gate: build only when something that ends up in
+    # the APK changed. versionCode is the commit count, so skipped pushes
+    # still leave it monotonic.
+    paths:
+      - 'app/**'
+      - '.fvmrc'
+      - '.versioncode-offset'
+      - '.github/workflows/release-apk.yml'
   # Lets a release be rebuilt from the current main without a dummy commit.
   workflow_dispatch:
 
@@ -47,6 +55,8 @@ jobs:
         with:
           distribution: temurin
           java-version: "17"
+          # ~/.gradle caches + wrapper, keyed on the Gradle files.
+          cache: gradle
 
       - uses: subosito/flutter-action@v2
         with:

app/pubspec.yaml

@@ -2,7 +2,7 @@ name: diet_guard_app
 description: "Companion phone app for diet_guard: log meals on the go."
 publish_to: 'none'
 
-version: 1.0.98+1
+version: 1.0.99+1
 
 environment:
   sdk: ^3.12.2