Add full app source

Adds the Flutter inventory app source, cleaned up for a shared repo:
generic package name, no hardcoded ERP endpoints (moved to gitignored
local config), no dead auth code, no debug logging of session data.

android/settings.gradle.kts

@@ -0,0 +1,25 @@
+pluginManagement {
+    val flutterSdkPath = run {
+        val properties = java.util.Properties()
+        file("local.properties").inputStream().use { properties.load(it) }
+        val flutterSdkPath = properties.getProperty("flutter.sdk")
+        require(flutterSdkPath != null) { "flutter.sdk not set in local.properties" }
+        flutterSdkPath
+    }
+
+    includeBuild("$flutterSdkPath/packages/flutter_tools/gradle")
+
+    repositories {
+        google()
+        mavenCentral()
+        gradlePluginPortal()
+    }
+}
+
+plugins {
+    id("dev.flutter.flutter-plugin-loader") version "1.0.0"
+    id("com.android.application") version "8.7.0" apply false
+    id("org.jetbrains.kotlin.android") version "1.8.22" apply false
+}
+
+include(":app")