CI: fix release APK upload (signed optional)

Extension Box is a modular Android system monitoring application built around independently controlled extensions. The app runs a foreground monitoring service and displays live system data through a persistent notification and in-app dashboard cards. Each module can be enabled or disabled individually. Disabled modules do not execute background logic. Current Features 🔋 Battery Current (mA) Power (W) Temperature Health Voltage (when available) 🧠 CPU & RAM CPU usage Memory usage 📱 Screen Time Screen on time Screen off time Drain rates 😴 Deep Sleep Awake ratio Deep sleep ratio 📶 Network Speed Real-time download speed Real-time upload speed 📊 Data Usage Daily usage Monthly usage WiFi & mobile breakdown 🔓 Unlock Counter Daily unlock count Usage awareness tracking 💾 Storage Internal storage usage 📡 Connection Info WiFi state Cellular state VPN detection 🕒 Uptime Device uptime since boot 👣 Step Counter Step count Distance (sensor-based) 🏎 Speed Test Manual or periodic network speed testing 🍆 Fap Counter Self-monitoring counter Streak tracking