Add rtl_tcp_andro as submodule for SDR driver app

RTL-SDR + HackRF native Android driver (iqsrc:// protocol).
Auto-installs APK during module flash if built. Build docs
updated with instructions.

customize.sh

@@ -46,6 +46,21 @@ echo "24M:1800M" > "$MODPATH/config/spectrum_range"
 mkdir -p "$MODPATH/modules"
 mkdir -p "$MODPATH/firmware"
 
+# Install rtl_tcp_andro APK if built
+RTL_APK="$MODPATH/apk/rtl_tcp_andro.apk"
+if [ -f "$RTL_APK" ]; then
+    pm install -r "$RTL_APK" 2>/dev/null
+    if [ $? -eq 0 ]; then
+        ui_print "- RTL-SDR + HackRF driver app installed"
+    else
+        ui_print "! Failed to install RTL-SDR driver app"
+        ui_print "! Install manually from apk/ directory"
+    fi
+else
+    ui_print "- RTL-SDR driver app not built yet"
+    ui_print "  Build with: cd tools/rtl_tcp_andro && ./gradlew assembleRelease"
+fi
+
 ui_print "- Default config written"
 ui_print "- Kernel module dir: modules/"
 ui_print "- Firmware dir: firmware/"