chore(release): v1.7.2 - Critical Bugfixes & Performance Improvements

CRITICAL BUGFIXES:
- IMPL_014: JSON/Markdown Timestamp Sync - Server mtime source of truth
- IMPL_015: SyncStatus PENDING Fix - Set before JSON serialization
- IMPL_001: Deletion Tracker Race Condition - Mutex-based sync
- IMPL_002: ISO8601 Timezone Parsing - Multi-format support
- IMPL_003: Memory Leak Prevention - SafeSardine Closeable
- IMPL_004: E-Tag Batch Caching - ~50-100ms performance gain

FEATURES:
- Auto-updating timestamps in UI (every 30s)
- Performance optimizations for Staggered Grid scrolling

BUILD:
- versionCode: 19
- versionName: 1.7.2

This release prepares for a new cross-platform Markdown editor
(Web, Desktop Windows + Linux, Mobile) with proper JSON ↔ Markdown synchronization
and resolves critical sync issues for external editor integration.

android/app/src/main/java/dev/dettmer/simplenotes/SimpleNotesApplication.kt

@@ -2,7 +2,6 @@ package dev.dettmer.simplenotes
 
 import android.app.Application
 import android.content.Context
-import androidx.appcompat.app.AppCompatDelegate
 import dev.dettmer.simplenotes.utils.Logger
 import dev.dettmer.simplenotes.sync.NetworkMonitor
 import dev.dettmer.simplenotes.utils.NotificationHelper