chore(01-01): scaffold Flutter project with all dependencies and tooling

- Flutter project created with flutter create (Android platform)
- Runtime deps: flutter_riverpod, riverpod_annotation, drift 2.31, drift_flutter, go_router, path_provider, shared_preferences, flutter_localizations, intl
- Dev deps: riverpod_generator, drift_dev 2.31, build_runner
- Pinned drift/drift_dev to 2.31 for analyzer ^9.0.0 compatibility with riverpod_generator
- Configured l10n.yaml, build.yaml (Drift), analysis_options.yaml (riverpod_lint)
- Minimal ARB file for localization tooling to resolve

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

android/app/src/main/res/drawable-v21/launch_background.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!-- Modify this file to customize your launch splash screen -->
+<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
+    <item android:drawable="?android:colorBackground" />
+
+    <!-- You can insert your own image assets here -->
+    <!-- <item>
+        <bitmap
+            android:gravity="center"
+            android:src="@mipmap/launch_image" />
+    </item> -->
+</layer-list>