🔐 Add keystore management scripts and documentation [skip ci]

- Add create-keystore.fish: Generate new release keystore with auto-generated passwords
- Add verify-secrets.fish: Verify GitHub Secrets and local keystore setup
- Add build-release-local.fish: Build signed release APKs locally
- Add LOCAL_BUILDS.md: Documentation for local release builds
- Add key.properties.example: Template for signing configuration
- Update android/.gitignore: Protect sensitive keystore files
- Integrate GitHub CLI for automatic secret management
- All scripts support both manual and automated workflows

android/scripts/build-release-local.fish

@@ -0,0 +1,104 @@
+#!/usr/bin/env fish
+
+# Simple Notes Sync - Lokaler Release Build
+# Erstellt signierte APKs, die mit GitHub Release-APKs kompatibel sind
+
+set -l SCRIPT_DIR (dirname (status --current-filename))
+set -l ANDROID_DIR (realpath "$SCRIPT_DIR/..")
+set -l KEY_PROPERTIES "$ANDROID_DIR/key.properties"
+
+echo "🔨 Simple Notes Sync - Lokaler Release Build"
+echo ""
+
+# 1. Prüfe ob key.properties existiert
+if not test -f "$KEY_PROPERTIES"
+    echo "❌ Fehler: key.properties nicht gefunden!"
+    echo ""
+    echo "Bitte erstelle die Datei:"
+    echo "  cd $ANDROID_DIR"
+    echo "  cp key.properties.example key.properties"
+    echo ""
+    echo "Und fülle sie mit den echten Keystore-Daten aus."
+    echo "Siehe: android/LOCAL_BUILDS.md"
+    exit 1
+end
+
+# 2. Prüfe ob Keystore existiert
+set -l KEYSTORE "$ANDROID_DIR/app/simple-notes-release.jks"
+if not test -f "$KEYSTORE"
+    echo "❌ Fehler: Keystore nicht gefunden!"
+    echo "  Erwartet: $KEYSTORE"
+    exit 1
+end
+
+echo "✅ key.properties gefunden"
+echo "✅ Keystore gefunden"
+echo ""
+
+# 3. Build-Typ abfragen
+echo "Welchen Build möchtest du erstellen?"
+echo "  1) Standard Flavor (empfohlen)"
+echo "  2) F-Droid Flavor"
+echo "  3) Beide Flavors"
+echo ""
+read -P "Auswahl [1-3]: " -n 1 choice
+
+echo ""
+echo ""
+
+switch $choice
+    case 1
+        echo "🏗️  Baue Standard Release APKs..."
+        cd "$ANDROID_DIR"
+        ./gradlew assembleStandardRelease --no-daemon
+        
+        if test $status -eq 0
+            echo ""
+            echo "✅ Build erfolgreich!"
+            echo ""
+            echo "📦 APKs findest du hier:"
+            echo "  $ANDROID_DIR/app/build/outputs/apk/standard/release/"
+            ls -lh "$ANDROID_DIR/app/build/outputs/apk/standard/release/"*.apk
+        end
+        
+    case 2
+        echo "🏗️  Baue F-Droid Release APKs..."
+        cd "$ANDROID_DIR"
+        ./gradlew assembleFdroidRelease --no-daemon
+        
+        if test $status -eq 0
+            echo ""
+            echo "✅ Build erfolgreich!"
+            echo ""
+            echo "📦 APKs findest du hier:"
+            echo "  $ANDROID_DIR/app/build/outputs/apk/fdroid/release/"
+            ls -lh "$ANDROID_DIR/app/build/outputs/apk/fdroid/release/"*.apk
+        end
+        
+    case 3
+        echo "🏗️  Baue Standard + F-Droid Release APKs..."
+        cd "$ANDROID_DIR"
+        ./gradlew assembleStandardRelease assembleFdroidRelease --no-daemon
+        
+        if test $status -eq 0
+            echo ""
+            echo "✅ Build erfolgreich!"
+            echo ""
+            echo "📦 Standard APKs:"
+            echo "  $ANDROID_DIR/app/build/outputs/apk/standard/release/"
+            ls -lh "$ANDROID_DIR/app/build/outputs/apk/standard/release/"*.apk
+            echo ""
+            echo "📦 F-Droid APKs:"
+            echo "  $ANDROID_DIR/app/build/outputs/apk/fdroid/release/"
+            ls -lh "$ANDROID_DIR/app/build/outputs/apk/fdroid/release/"*.apk
+        end
+        
+    case '*'
+        echo "❌ Ungültige Auswahl"
+        exit 1
+end
+
+echo ""
+echo "💡 Tipp: Du kannst die APK per HTTP Server verteilen:"
+echo "   cd app/build/outputs/apk/standard/release"
+echo "   python3 -m http.server 8892"