feat: add demo mode for testing and review purposes

- Activates by tapping "None (disable)" 7 times.
- Displays a confirmation message when `Demo Mode` is enabled.
- Simulates a connection to a Meshtastic device and allows the app to function without requiring real hardware.

app/src/main/java/com/geeksville/mesh/repository/radio/MockInterfaceSpec.kt

@@ -1,15 +1,11 @@
 package com.geeksville.mesh.repository.radio
 
-import android.app.Application
-import com.geeksville.mesh.android.BuildUtils
-import com.geeksville.mesh.android.GeeksvilleApplication
 import javax.inject.Inject
 
 /**
  * Mock interface backend implementation.
  */
 class MockInterfaceSpec @Inject constructor(
-    private val application: Application,
     private val factory: MockInterfaceFactory
 ): InterfaceSpec<MockInterface> {
     override fun createInterface(rest: String): MockInterface {
@@ -17,6 +13,5 @@ class MockInterfaceSpec @Inject constructor(
     }
 
     /** Return true if this address is still acceptable. For BLE that means, still bonded */
-    override fun addressValid(rest: String): Boolean =
-        BuildUtils.isEmulator || ((application as GeeksvilleApplication).isInTestLab)
-}
+    override fun addressValid(rest: String): Boolean = true
+}

app/src/main/java/com/geeksville/mesh/repository/radio/RadioInterfaceService.kt

@@ -7,6 +7,7 @@ import androidx.lifecycle.Lifecycle
 import androidx.lifecycle.coroutineScope
 import com.geeksville.mesh.CoroutineDispatchers
 import com.geeksville.mesh.android.BinaryLogFile
+import com.geeksville.mesh.android.BuildUtils
 import com.geeksville.mesh.android.GeeksvilleApplication
 import com.geeksville.mesh.android.Logging
 import com.geeksville.mesh.concurrent.handledLaunch
@@ -104,8 +105,8 @@ class RadioInterfaceService @Inject constructor(
         return interfaceFactory.toInterfaceAddress(interfaceId, rest)
     }
 
-    fun isAddressValid(address: String?): Boolean {
-        return interfaceFactory.addressValid(address)
+    val isMockInterface: Boolean by lazy {
+        BuildUtils.isEmulator || (context as GeeksvilleApplication).isInTestLab
     }
 
     /** Return the device we are configured to use, or null for none
@@ -121,7 +122,7 @@ class RadioInterfaceService @Inject constructor(
         var address = prefs.getString(DEVADDR_KEY, null)
 
         // If we are running on the emulator we default to the mock interface, so we can have some data to show to the user
-        if (address == null && isAddressValid(mockInterfaceAddress)) {
+        if (address == null && isMockInterface) {
             address = mockInterfaceAddress
         }