Fix connection leaks causing crash on Android 9

- Added SafeSardineWrapper to properly close HTTP responses
- Prevents resource exhaustion after extended use (30-45 min)
- Added preemptive authentication to reduce 401 round-trips
- Added ProGuard rule for TextInclusionStrategy warnings
- Updated version to 1.7.1

Refs: #15

android/app/build.gradle.kts

@@ -20,8 +20,8 @@ android {
         applicationId = "dev.dettmer.simplenotes"
         minSdk = 24
         targetSdk = 36
-        versionCode = 17  // 🎨 v1.7.0: Grid Layout + Backup Encryption
-        versionName = "1.7.0"  // 🎨 v1.7.0: Grid Layout + Backup Encryption
+        versionCode = 18  // 🔧 v1.7.1: Connection Leak Fix (Issue #15)
+        versionName = "1.7.1"  // 🔧 v1.7.1: Connection Leak Fix
 
         testInstrumentationRunner = "androidx.test.runner.AndroidJUnitRunner"
     }