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/infrastructure/persistence/sqlite/migrations.go

@@ -56,7 +56,6 @@ CREATE TABLE IF NOT EXISTS habit_entries (
 	scheduled_date DATE NOT NULL,
 	completed_at DATETIME NOT NULL,
 	value REAL,
-	deleted_at DATETIME,
 	FOREIGN KEY (habit_id) REFERENCES habits(id) ON DELETE CASCADE,
 	UNIQUE(habit_id, scheduled_date)
 );
@@ -67,5 +66,4 @@ CREATE INDEX IF NOT EXISTS idx_habits_user ON habits(user_id);
 CREATE INDEX IF NOT EXISTS idx_habits_active ON habits(user_id, archived_at);
 CREATE INDEX IF NOT EXISTS idx_entries_habit ON habit_entries(habit_id);
 CREATE INDEX IF NOT EXISTS idx_entries_scheduled ON habit_entries(scheduled_date);
-CREATE INDEX IF NOT EXISTS idx_entries_deleted ON habit_entries(deleted_at);
 `