fix(auth): initialize AuthManager in custom application class (#172)

Closes #68. Redundant initialization in MainActivity has been removed.

app/src/main/java/com/m57/hermescontrol/HermesControlApp.kt

@@ -0,0 +1,11 @@
+package com.m57.hermescontrol
+
+import android.app.Application
+import com.m57.hermescontrol.data.local.AuthManager
+
+class HermesControlApp : Application() {
+    override fun onCreate() {
+        super.onCreate()
+        AuthManager.init(this)
+    }
+}

app/src/main/java/com/m57/hermescontrol/MainActivity.kt

@@ -16,8 +16,6 @@ class MainActivity : ComponentActivity() {
     override fun onCreate(savedInstanceState: Bundle?) {
         super.onCreate(savedInstanceState)
 
-        AuthManager.init(this)
-
         // Read notification tap sessionId (if any) from the intent that launched us
         val notificationSessionId = intent?.getStringExtra(NotificationReplyReceiver.EXTRA_SESSION_ID)