feat(proguard): IMPL_07 - Add missing Widget & Compose ProGuard rules

- Add Widget ActionCallback rules to prevent R8 removal (fixes potential widget crashes)
- Add Glance state preservation rules for widget preferences
- Add Compose TextLayout rules to prevent gradient regression in release builds
- Bump version to 1.8.1 (versionCode 21, versionName "1.8.1")

Fixes:
- Widget actions (ToggleChecklistItemAction, etc.) could be stripped by R8
- Glance widget state (DataStore-based) needs reflection protection
- Compose onTextLayout callbacks could be optimized away causing gradient issues

Files changed:
- android/app/proguard-rules.pro: Added v1.8.1 rules section (+17 lines)
- android/app/build.gradle.kts: Version bump 1.8.0 → 1.8.1

android/app/build.gradle.kts

@@ -20,8 +20,8 @@ android {
         applicationId = "dev.dettmer.simplenotes"
         minSdk = 24
         targetSdk = 36
-        versionCode = 20  // 🎉 v1.8.0: Widgets, Sorting, UI Polish, Post-Update Changelog
+        versionCode = 21  // 🐛 v1.8.1: Checklist Fixes, Widget Sorting, ProGuard Audit
-        versionName = "1.8.0"  // 🎉 v1.8.0: Major Feature Release
+        versionName = "1.8.1"  // 🐛 v1.8.1: Bugfix & Polish Release
 
         testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
     }

android/app/proguard-rules.pro

@@ -82,3 +82,23 @@
 # v1.7.1: Suppress TextInclusionStrategy warnings on older Android versions
 # This class only exists on API 35+ but Compose handles the fallback gracefully
 -dontwarn android.text.Layout$TextInclusionStrategy
+
+# ═══════════════════════════════════════════════════════════════════════
+# v1.8.1: Widget & Compose Fixes
+# ═══════════════════════════════════════════════════════════════════════
+
+# Glance Widget ActionCallbacks (instanziiert via Reflection durch actionRunCallback<T>())
+# Ohne diese Rule findet R8 die Klassen nicht zur Laufzeit → Widget-Crash
+-keep class dev.dettmer.simplenotes.widget.*Action { *; }
+-keep class dev.dettmer.simplenotes.widget.*Receiver { *; }
+
+# Glance Widget State (Preferences-basiert, intern via Reflection)
+-keep class androidx.glance.appwidget.state.** { *; }
+-keep class androidx.datastore.preferences.** { *; }
+
+# Compose Text Layout: Verhindert dass R8 onTextLayout-Callbacks
+# als Side-Effect-Free optimiert (behebt Gradient-Regression)
+-keepclassmembers class androidx.compose.foundation.text.** {
+    <methods>;
+}
+-keep class androidx.compose.ui.text.TextLayoutResult { *; }