feat: implement multi-step mood logging wizard

Adds sleep/energy/positivity/self-worth tracking columns to the database
(schema v2 migration), a new 5-option StepScale widget, per-answer chips
at the top of the screen, a 2×2 activity grid chip, and a full step-by-step
wizard flow: mood → sleep (first entry today only) → energy → positivity →
self-worth → activities → review+save.

lib/core/database/daos/mood_dao.dart

@@ -74,6 +74,16 @@ class MoodDao extends DatabaseAccessor<AppDatabase> with _$MoodDaoMixin {
             ..orderBy([(t) => OrderingTerm.asc(t.timestamp)]))
           .get();
 
+  Future<bool> hasEntryToday() async {
+    final today = DateTime.now();
+    final start = DateTime(today.year, today.month, today.day);
+    final end = start.add(const Duration(days: 1));
+    return (await (select(moodEntries)
+          ..where((t) => t.timestamp.isBetweenValues(start, end))
+          ..limit(1))
+        .getSingleOrNull()) != null;
+  }
+
   // Average mood per day — used by calendar heatmap
   Future<Map<DateTime, double>> getDailyAverages(
       DateTime start, DateTime end) async {