M2b: Android skeleton, :core:model contract, :domain passing all vectors

Gradle project in android/ with every module of SPEC §6.2 (build-logic convention plugins, version catalog,
architecture check in check), :core:model types and repository interfaces of §14.2.4 and §14.5, :domain
implementing §14.5.2 and §14.5.4 (125 vector cases), scenario-driven fakes with the empty scenario, Room 3
entities and KvittDatabase v1 with exported schema, :app shell with Hilt, en/sv strings with MissingTranslation
as a lint error, Roborazzi goldens of the empty screen in light and dark.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

android/feature/onboarding/build.gradle.kts

@@ -0,0 +1,4 @@
+// :feature:onboarding — Pairing, partner profile step, waiting for partner, device removed (S-1, S-2, S-3, S-18; M7a). Convention: android/README.md.
+plugins {
+    id("kvitt.android.feature")
+}

android/feature/onboarding/src/main/kotlin/se/hagstedt/kvitt/feature/onboarding/OnboardingEntry.kt

@@ -0,0 +1,14 @@
+package se.hagstedt.kvitt.feature.onboarding
+
+import androidx.compose.foundation.layout.Box
+import androidx.compose.runtime.Composable
+import androidx.compose.ui.Modifier
+
+/**
+ * Module shell from M2b: the feature's entry point. The owning milestone replaces it with one composable per screen
+ * that takes its Hilt ViewModel (`hiltViewModel()`) by default and navigation as plain lambdas (android/README.md).
+ */
+@Composable
+fun OnboardingEntry(modifier: Modifier = Modifier) {
+    Box(modifier)
+}