⚙️ FEATURE-#11: Move AppendedUID and IMAPHost to email_profile.types

[FernandoCelmer]

Closes #11

Summary

Both AppendedUID and IMAPHost are return-type value objects that the user rarely instantiates directly. Moving them to a dedicated email_profile/types.py module makes their role explicit and keeps mailbox.py / providers.py focused on behaviour.

Backwards compatibility

Existing imports keep working — mailbox.py and providers.py re-export the symbols:

from email_profile.mailbox import AppendedUID   # still works
from email_profile.providers import IMAPHost    # still works
from email_profile.types import AppendedUID, IMAPHost   # new canonical location

Changes

• email_profile/types.py (new) — holds the two frozen dataclasses.
• email_profile/mailbox.py — imports AppendedUID from types; definition removed locally.
• email_profile/providers.py — imports IMAPHost from types; definition removed locally.

Test plan

• 131 tests pass
• ruff + format clean