feat(liquibase-xml): extract inline FK constraints and map Liquibase types

- Extract foreign key constraints from <constraints> elements inside
  <column> tags (foreignKeyName, referencedTableName, referencedColumnNames)
  and generate ALTER TABLE ADD CONSTRAINT statements
- Add map_liquibase_type() to translate abstract Liquibase types (datetime,
  int, number, decimal, currency, clob, blob, etc.) to PostgreSQL equivalents
- Apply type mapping at all column type read sites including modifyDataType
- Extract shared parse_column_element() and parse_column_constraints() helpers
  to deduplicate column parsing between createTable and addColumn handlers
- Warn and skip inline FKs missing referencedColumnNames instead of guessing
- Add 10 new tests covering inline FK generation, type mapping, and edge cases

Author: sj-robert