Codex Usage v0.1.16

What's changed

• Keeps the latest Codex usage percentage in a persistent notification and Android 16 status-bar chip.
• Refreshes every 15 minutes and when the app opens, the phone unlocks, or connectivity returns.
• Replaces change notifications instead of stacking one per percentage update.
• Adds native light/dark themes and removes interval/percentage controls from the main screen.