Format the "updated" timestamp as a locale-aware date/time

Replaces the raw "2026-09-10 10:03:54" with each platform's own
locale-formatted, no-seconds rendering (e.g. "Sep 10, 2026, 10:03 AM"
in en-US) — mirroring how amounts are already locale-formatted
elsewhere (NumberFormat.kt). Android uses the pre-java.time
Calendar/DateFormat APIs since minSdk 24 predates java.time (API 26)
and the project has no core library desugaring configured.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FXcrACM5sok3M1KQJ8kByy

shared/src/jvmMain/kotlin/xyz/tyiu/satsprice/domain/DateFormat.jvm.kt

@@ -0,0 +1,13 @@
+package xyz.tyiu.satsprice.domain
+
+import kotlinx.datetime.LocalDateTime
+import kotlinx.datetime.toJavaLocalDateTime
+import java.time.format.DateTimeFormatter
+import java.time.format.FormatStyle
+import java.util.Locale
+
+actual fun localizedDateTime(dateTime: LocalDateTime): String {
+    val formatter = DateTimeFormatter.ofLocalizedDateTime(FormatStyle.MEDIUM, FormatStyle.SHORT)
+        .withLocale(Locale.getDefault())
+    return dateTime.toJavaLocalDateTime().format(formatter)
+}