feat(01-01): add core infrastructure, localization, and Wave 0 tests

- AppDatabase with schemaVersion 1, in-memory executor for testing
- Database provider with @Riverpod(keepAlive: true)
- AppTheme with sage green seed ColorScheme and warm surface overrides
- ThemeNotifier with SharedPreferences persistence, defaults to system
- Full German ARB localization (15 keys) with proper umlauts
- Minimal main.dart with ProviderScope placeholder
- Drift schema v1 captured via make-migrations
- All .g.dart files generated via build_runner
- Wave 0 tests: database (3), color scheme (6), theme (3), localization (2) -- 14 total, all passing

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

lib/core/theme/theme_provider.g.dart

@@ -0,0 +1,62 @@
+// GENERATED CODE - DO NOT MODIFY BY HAND
+
+part of 'theme_provider.dart';
+
+// **************************************************************************
+// RiverpodGenerator
+// **************************************************************************
+
+// GENERATED CODE - DO NOT MODIFY BY HAND
+// ignore_for_file: type=lint, type=warning
+
+@ProviderFor(ThemeNotifier)
+final themeProvider = ThemeNotifierProvider._();
+
+final class ThemeNotifierProvider
+    extends $NotifierProvider<ThemeNotifier, ThemeMode> {
+  ThemeNotifierProvider._()
+    : super(
+        from: null,
+        argument: null,
+        retry: null,
+        name: r'themeProvider',
+        isAutoDispose: true,
+        dependencies: null,
+        $allTransitiveDependencies: null,
+      );
+
+  @override
+  String debugGetCreateSourceHash() => _$themeNotifierHash();
+
+  @$internal
+  @override
+  ThemeNotifier create() => ThemeNotifier();
+
+  /// {@macro riverpod.override_with_value}
+  Override overrideWithValue(ThemeMode value) {
+    return $ProviderOverride(
+      origin: this,
+      providerOverride: $SyncValueProvider<ThemeMode>(value),
+    );
+  }
+}
+
+String _$themeNotifierHash() => r'060f7d104905995da8c785d2f50f15a4db2d7022';
+
+abstract class _$ThemeNotifier extends $Notifier<ThemeMode> {
+  ThemeMode build();
+  @$mustCallSuper
+  @override
+  void runBuild() {
+    final ref = this.ref as $Ref<ThemeMode, ThemeMode>;
+    final element =
+        ref.element
+            as $ClassProviderElement<
+              AnyNotifier<ThemeMode, ThemeMode>,
+              ThemeMode,
+              Object?,
+              Object?
+            >;
+    element.handleCreate(ref, build);
+  }
+}