Summary

• Fix thread-unsafe shared RelativeDateTimeFormatter instance that caused memory corruption when accessed from multiple threads concurrently
• Cache battery percentage values to local variables before passing to both icon and label functions, reducing repeated interface dispatch chains
• Replace per-type getBatteryLevel* extension functions with a single formatBatteryPercent helper

Context

Multiple native crashes (SIGSEGV in ART) were reported in PodDeviceExtensionsKt functions during RecyclerView binding and notification building on background threads. The shared static RelativeDateTimeFormatter is not thread-safe and was the most likely cause of heap corruption. Battery percentage caching is an additional hardening measure.

Test plan

• ./gradlew assembleFossDebug compiles
• ./gradlew testFossDebugUnitTest passes
• Verify battery icons/labels in overview, notification, popup, and widget