refactor: derive __version__ from package metadata (single source)

Signed-off-by: disqualifier <dev@disqualifier.me>

src/aiomail/__init__.py

@@ -8,6 +8,8 @@ connect/reconnect lock; sequence-number ids from before a reconnect are invalid
 (pass use_uid=True if ids must survive one); credentials are always caller-supplied via
 an injected Auth, never read from config.
 """
+from importlib.metadata import version, PackageNotFoundError
+
 from .auth import Auth, OAuth2Auth, PasswordAuth
 from .client import IMAPClient
 from .extract import (
@@ -35,4 +37,7 @@ __all__ = [
     "DEFAULT_FOLDERS",
 ]
 
-__version__ = "0.1.10"
+try:
+    __version__ = version("aiomail")
+except PackageNotFoundError:
+    __version__ = "0.0.0+unknown"