feat(parser): implement RFC 5322 address parser with CFWS and obsolete forms

[partyplatter08-lab]

Summary

• Add a pure-stdlib AddressParser and RFC5322Address model for RFC 5322 mailbox, group, address-list, and mailbox-list parsing.
• Implement CFWS/comment extraction, quoted strings, quoted-pairs, dot-atoms, domain literals with IPv4/IPv6 validation, strict CFWS-only groups, and strict/permissive obsolete-addressing behavior.
• Add a compliance matrix mapping address-related ABNF productions from §3.2-§3.4.1 and §4.4 to parser methods and tests.
• Annotate source.md with parser implementation notes and CAP metadata at the relevant RFC grammar sections.

Tests

• python3 -m py_compile parser.py test_parser.py
• python3 -m unittest -v test_parser.py
• Local reproduction of .github/workflows/cap-validate.yml validation checks

[partyplatter08-lab]

Withdrawing this PR; I am no longer pursuing this change.