Refactor habit entries: remove soft delete and add smart pagination

Remove soft delete from HabitEntry:
- Eliminate DeletedAt field from entity and database
- Change UnmarkHabit from soft delete to hard delete
- Simplify all queries removing deleted_at checks
- Update migration to remove deleted_at column

Add date filtering and smart pagination to GetHabitEntries:
- Support optional from/to date parameters
- Implement intelligent pagination rules:
  * No date range: pagination required
  * Date range > 1 year: pagination required
  * Date range ≤ 1 year: pagination optional
- Pagination defaults (page=1, limit=50) only when required
- Return metadata with total count, page, and limit

Technical improvements:
- Cleaner codebase without soft delete complexity
- Better performance (no filtering in queries)
- More intuitive API with flexible pagination
- Comprehensive test coverage for validation rules

internal/application/queries/get_todays_habits.go

@@ -70,7 +70,7 @@ func (h *GetTodaysHabitsHandler) Handle(
 
 		isCompleted := false
 		for _, entry := range entries {
-			if entry.ScheduledDate.Equal(query.Date) && entry.DeletedAt == nil {
+			if entry.ScheduledDate.Equal(query.Date) {
 				isCompleted = true
 				break
 			}