feat: enhance builder and count queries

[cofin]

Bug Fixes

• sqlspec/driver/_common.py: Fixed _create_count_query() to pass **original_sql.named_parameters in both return statements (lines ~1488, 1494)

New Window Function Features

• sqlspec/builder/_factory.py:
  • Added count_over(), sum_over(), avg_over(), max_over(), min_over() methods
  • Added count_over_, sum_over_, avg_over_, max_over_, min_over_ properties
  • Added lag() and lead() methods with full parameter support (column, offset, default, partition_by, order_by)

Driver Enhancements

• sqlspec/driver/_async.py & _sync.py:
  • Added count_with_window: bool = False parameter to select_with_total()
  • Added _add_count_over_column() helper method for window function pagination

DDL Completeness

• sqlspec/builder/_ddl.py: Added DropMaterializedView class
• sqlspec/builder/_factory.py: Added drop_materialized_view() method