Remove dashboard/VPS references - make project PR-ready

- Remove DeviceRegistry.java (dashboard integration)
- Remove VPS IP from build.gradle
- Remove personal Gitea token from UpdateManager
- Add configurable UPDATE_CHECK_URL for updates
- Clean README to be generic and PR-ready
- Clean update manifests
- Remove Docker files and .env from repo

app/build.gradle

@@ -10,7 +10,7 @@ android {
         targetSdk 35
         versionCode 100111
         versionName "10.1.11"
-        buildConfigField "String", "DEVICE_REGISTRY_URL", '"http://194.163.191.200:4000"'
+        buildConfigField "String", "UPDATE_CHECK_URL", '""'
     }
 
     buildTypes {