feat(daemon): add async event bus for inter-plugin notifications

Adds daemon/events.py — a lightweight asyncio.Queue-based publish/subscribe
bus that lets daemon tasks communicate without direct imports between plugins.
Email plugin publishes new_email events; messaging bots consume via
subscribe_forever(). Also adds email optional-dependency group to pyproject.toml
(imap-tools, google-api-python-client, google-auth-oauthlib, O365).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

pyproject.toml

@@ -35,6 +35,12 @@ gdrive    = ["google-api-python-client>=2.120.0", "google-auth-oauthlib>=1.2.0"]
 onedrive  = ["msal>=1.28.0"]
 dropbox   = ["dropbox>=12.0.0"]
 daemon    = ["aiofiles>=23.0.0"]
+email     = [
+    "imap-tools>=1.7.0",
+    "google-api-python-client>=2.120.0",
+    "google-auth-oauthlib>=1.2.0",
+    "O365>=2.0.36",
+]
 all-plugins = [
     "caldav>=1.3.0", "webdav4>=0.9.0", "vobject>=0.9.6",
     "matrix-nio>=0.24.0", "aiofiles>=23.0.0",
@@ -44,6 +50,8 @@ all-plugins = [
     "google-api-python-client>=2.120.0", "google-auth-oauthlib>=1.2.0",
     "msal>=1.28.0",
     "dropbox>=12.0.0",
+    "imap-tools>=1.7.0",
+    "O365>=2.0.36",
 ]
 
 [project.scripts]