Add calendar invite actions to mail app with A/D/T keybindings

- Add calendar_invite.py with detect/find/respond functions for calendar invites
- Keybindings: A (accept), D (decline), T (tentative)
- Searches Graph API calendarView to find matching event by subject
- Responds via Graph API POST to event/{id}/accept|decline|tentativelyAccept

src/mail/app.py

@@ -8,6 +8,11 @@ from .screens.SearchPanel import SearchPanel
 from .actions.task import action_create_task
 from .actions.open import action_open
 from .actions.delete import delete_current
+from .actions.calendar_invite import (
+    action_accept_invite,
+    action_decline_invite,
+    action_tentative_invite,
+)
 from src.services.taskwarrior import client as taskwarrior_client
 from src.services.himalaya import client as himalaya_client
 from src.utils.shared_config import get_theme_name
@@ -134,6 +139,9 @@ class EmailViewerApp(App):
             Binding("escape", "clear_selection", "Clear selection"),
             Binding("/", "search", "Search"),
             Binding("u", "toggle_read", "Toggle read/unread"),
+            Binding("A", "accept_invite", "Accept invite"),
+            Binding("D", "decline_invite", "Decline invite"),
+            Binding("T", "tentative_invite", "Tentative"),
         ]
     )
 
@@ -854,6 +862,18 @@ class EmailViewerApp(App):
     def action_create_task(self) -> None:
         action_create_task(self)
 
+    def action_accept_invite(self) -> None:
+        """Accept the calendar invite from the current email."""
+        action_accept_invite(self)
+
+    def action_decline_invite(self) -> None:
+        """Decline the calendar invite from the current email."""
+        action_decline_invite(self)
+
+    def action_tentative_invite(self) -> None:
+        """Tentatively accept the calendar invite from the current email."""
+        action_tentative_invite(self)
+
     def action_open_links(self) -> None:
         """Open the link panel showing links from the current message."""
         content_container = self.query_one(ContentContainer)