Add React Native mobile app for Makima (#3)

* [WIP] Heartbeat checkpoint - 2026-01-18 02:58:27 UTC

* feat(mobile): complete mobile app integration and verification

- Add ThemeColors type export to Colors.ts for type safety
- Export SUPABASE_URL from supabase.ts and use environment variables
- Update .env.example with correct default URLs
- Add comprehensive README.md with setup instructions

Verified:
- TypeScript compiles without errors
- App exports successfully for iOS and Android
- All screens accessible (login, dashboard, tasks, settings, task detail)
- Auth flow working with Zustand store and Supabase

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* Task completion checkpoint

---------

Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

1 files changed, 31 insertions, 0 deletions

diff --git a/apps/mobile/app/(auth)/_layout.tsx b/apps/mobile/app/(auth)/_layout.tsx
new file mode 100644
index 0000000..1def062
--- /dev/null
+++ b/apps/mobile/app/(auth)/_layout.tsx
@@ -0,0 +1,31 @@
+import { Stack } from 'expo-router';
+import { useColorScheme } from 'react-native';
+import { Colors } from '../../constants/Colors';
+
+/**
+ * Auth group layout
+ * Provides stack navigation for authentication screens
+ */
+export default function AuthLayout() {
+  const colorScheme = useColorScheme() ?? 'dark';
+  const colors = Colors[colorScheme];
+
+  return (
+    <Stack
+      screenOptions={{
+        headerShown: false,
+        contentStyle: {
+          backgroundColor: colors.background,
+        },
+        animation: 'fade',
+      }}
+    >
+      <Stack.Screen
+        name="login"
+        options={{
+          title: 'Sign In',
+        }}
+      />
+    </Stack>
+  );
+}