feat: replace json tools with local data controls

lib/src/application/focus_seed_controller.dart

@@ -1,5 +1,3 @@
-import 'dart:convert';
-
 import 'package:flutter/foundation.dart';
 import 'package:flutter/services.dart';
 
@@ -168,22 +166,41 @@ class FocusSeedController extends ChangeNotifier {
     return _commit(current.copyWith(reflections: reflections));
   }
 
-  Future<bool> importState(String raw) async {
-    try {
-      final decoded = jsonDecode(raw);
-      if (decoded is! Map<String, dynamic>) {
-        return false;
-      }
-      return _commit(AppState.fromJson(decoded));
-    } on Object {
-      return false;
-    }
-  }
-
   Future<bool> clearData() async {
     return _commit(AppState.starter(defaultHabitTitles: _defaultHabitTitles));
   }
 
+  Future<bool> clearToday() async {
+    final current = _state;
+    if (current == null) {
+      return false;
+    }
+    final today = todayKey();
+    final habits = current.habits
+        .map(
+          (habit) => habit.copyWith(
+            completedDates: Set<String>.from(habit.completedDates)
+              ..remove(today),
+          ),
+        )
+        .toList(growable: false);
+    final sessions = current.sessions
+        .where((session) => dateKey(session.completedAt) != today)
+        .toList(growable: false);
+    final reflections = current.reflections
+        .where((reflection) => reflection.dateKey != today)
+        .toList(growable: false);
+    _analytics.track('today_cleared');
+    return _commit(
+      current.copyWith(
+        anchor: current.anchorDateKey == today ? '' : current.anchor,
+        habits: habits,
+        sessions: sessions,
+        reflections: reflections,
+      ),
+    );
+  }
+
   Future<bool> _commit(AppState nextState) async {
     final previousState = _state;
     _state = nextState;