fix(ci): scope flutter analyze to lib/ test/ + export ANDROID_HOME in build steps

1. flutter analyze was scanning the entire working directory including the
   downloaded Flutter SDK which has intentional errors. Scoped to lib/ test/.
2. ANDROID_HOME set in 'Install Android SDK' step does NOT persist to build
   steps. Added export ANDROID_HOME to both APK and AAB build steps.

.gitea/workflows/ci.yml

@@ -65,7 +65,7 @@ jobs:
       - name: Analyze Dart code
         run: |
           export PATH="$PWD/flutter/bin:$PATH"
-          flutter analyze
+          flutter analyze lib/ test/
 
       - name: Auto-format source
         run: |
@@ -188,12 +188,14 @@ jobs:
       - name: Build APK (release)
         run: |
           export JAVA_HOME="$HOME/jdk"
+          export ANDROID_HOME="${HOME}/android-sdk"
           export PATH="$PWD/flutter/bin:$PATH"
           flutter build apk --release
 
       - name: Build App Bundle (release)
         run: |
           export JAVA_HOME="$HOME/jdk"
+          export ANDROID_HOME="${HOME}/android-sdk"
           export PATH="$PWD/flutter/bin:$PATH"
           flutter build appbundle --release