[MadDERt]

Summary

• Add faers_restrict() to filter reports by quarter, date window, sex,
  age, age group, and occurrence country. Supports intersected conditions,
  inverted selection, and partial-date handling.
• Add .role_cod to ordinary and stratified scans to restrict drug
  exposure counting while preserving background report counts.
• Support memory and DuckDB backends without modifying the input object.
• Update documentation, examples, and NEWS. No new dependencies.

Validation

• Relevant repository tests passed on both backends, with warnings recorded.
• Additional local regression tests: 36 groups passed.
• Real-data memory workflow: 68 checks passed on 456,337 reports,
  including independent count checks and input preservation.

[ShixiangWang]

@MadDERt 确认可以合并了你就自己合并下哈