Add app source and tests

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

lib/Peach/configs/Navigator.dart

@@ -0,0 +1,73 @@
+import 'package:flutter/material.dart';
+import 'package:page_transition/page_transition.dart';
+
+import '../about/internal/application/NavigatorType.dart';
+
+/// Every screen transition in the app funnels through here. Destinations are
+/// widget instances, not route names — there is no route table. Keeping one
+/// choke point means a guard (session, device, connectivity) can be applied to
+/// all routing by editing a single method.
+class PeachNavigation {
+  void navigateToPage(NavigatorType type, dynamic path, BuildContext context) {
+    _runSec(context, type, path);
+  }
+
+  Future _runSec(BuildContext context, NavigatorType type, dynamic path) async {
+    switch (type) {
+      case NavigatorType.openFully:
+        Navigator.of(context).pushReplacement(
+          MaterialPageRoute(builder: (BuildContext context) => path),
+        );
+        break;
+      case NavigatorType.justOpen:
+        Navigator.push(
+          context,
+          PageTransition(
+            type: PageTransitionType.size,
+            alignment: Alignment.center,
+            opaque: true,
+            child: path,
+          ),
+        );
+        break;
+      case NavigatorType.replaceCurrent:
+        Navigator.pushReplacement(
+          context,
+          PageTransition(
+            type: PageTransitionType.scale,
+            alignment: Alignment.center,
+            opaque: true,
+            curve: Curves.ease,
+            duration: const Duration(microseconds: 9000),
+            child: path,
+          ),
+        );
+        break;
+      case NavigatorType.makeNewMain:
+        Navigator.pushAndRemoveUntil(
+          context,
+          PageTransition(
+            type: PageTransitionType.fade,
+            alignment: Alignment.center,
+            opaque: true,
+            child: path,
+          ),
+          ModalRoute.withName('/'),
+        );
+        break;
+    }
+  }
+
+  /// Opens [path] and returns whatever it pops with — the reload-on-return
+  /// channel: a child calls `Navigator.pop(context, true)` and the parent
+  /// refreshes on a truthy result.
+  Future<dynamic> navigateToPageWithData(
+    dynamic path,
+    BuildContext context,
+  ) async {
+    return await Navigator.push(
+      context,
+      MaterialPageRoute(builder: (context) => path),
+    );
+  }
+}

lib/Peach/configs/ThemeController.dart

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+import 'package:flutter/material.dart';
+
+/// App-wide theme mode. `main.dart` listens to this and rebuilds MaterialApp;
+/// any screen can set it. Persisting the choice is the ViewModel's job — this
+/// only carries the live value.
+class ThemeController {
+  ThemeController._();
+
+  static final ValueNotifier<ThemeMode> mode = ValueNotifier<ThemeMode>(
+    ThemeMode.dark,
+  );
+
+  /// The stored string ('dark' | 'light' | 'system') for the current mode.
+  static String get name => mode.value.name;
+
+  static void apply(String stored) {
+    mode.value = switch (stored) {
+      'light' => ThemeMode.light,
+      'system' => ThemeMode.system,
+      _ => ThemeMode.dark,
+    };
+  }
+}