fix(caldav): point-event round-trip, recurrence push, delete propagation

Drift-audit Group 5 #7/#8 + Group 7 (CalDAV write-path):

- Point events no longer fabricate a 60-min DTEND: caldav.create_event emits
  DTSTART-only when there's no end and no duration, so the next pull doesn't
  read it back as duration_minutes=60 and silently lengthen the event.
- Recurrence edits now propagate: caldav.update_event gains a recurrence param
  (sentinel = leave unchanged; value/empty = set/clear RRULE), and _push_update
  passes the local event's rule so a changed/cleared RRULE isn't overwritten
  by the stale remote rule on the next pull.
- Event deletions propagate to CalDAV: trash.delete captures an event's
  caldav_uid before soft-deleting and fires _push_delete, so a UI/MCP delete
  removes the remote copy instead of leaving it to linger. (delete_event the
  service primitive is kept — still tested/usable — rather than removed.)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/fabledassistant/services/caldav.py

@@ -14,6 +14,10 @@ logger = logging.getLogger(__name__)
 
 CALDAV_SETTING_KEYS = ["caldav_url", "caldav_username", "caldav_password", "caldav_calendar_name", "caldav_timezone"]
 
+# Sentinel: distinguishes "leave the RRULE untouched" from "clear it" (None/"")
+# in update_event, since None is a meaningful value for recurrence.
+_RECURRENCE_UNSET = object()
+
 
 async def get_caldav_config(user_id: int) -> dict[str, str]:
     """Return the user's CalDAV config from their settings."""
@@ -214,14 +218,22 @@ async def create_event(
         result_end = d_end.isoformat()
     else:
         dt_start = _apply_timezone(datetime.fromisoformat(start), tz)
+        event.add("dtstart", dt_start)
+        result_start = dt_start.isoformat()
         if end:
             dt_end = _apply_timezone(datetime.fromisoformat(end), tz)
+        elif duration:
+            dt_end = dt_start + timedelta(minutes=duration)
         else:
-            dt_end = dt_start + timedelta(minutes=duration or 60)
-        event.add("dtstart", dt_start)
-        event.add("dtend", dt_end)
-        result_start = dt_start.isoformat()
-        result_end = dt_end.isoformat()
+            dt_end = None
+        if dt_end is not None:
+            event.add("dtend", dt_end)
+            result_end = dt_end.isoformat()
+        else:
+            # Point event (no end, no duration): emit DTSTART only. Fabricating
+            # a 60-min DTEND here would round-trip back on the next pull as
+            # duration_minutes=60, silently lengthening a point event.
+            result_end = None
 
     if description:
         event.add("description", description)
@@ -325,8 +337,14 @@ async def update_event(
     location: str | None = None,
     timezone: str | None = None,
     calendar_name: str | None = None,
+    recurrence: str | None | object = _RECURRENCE_UNSET,
 ) -> dict:
-    """Update a calendar event matching the query."""
+    """Update a calendar event matching the query.
+
+    ``recurrence``: leave at the sentinel to keep the existing RRULE; pass an
+    RRULE string to set it, or None/"" to remove it. The push path passes the
+    local event's recurrence so RRULE edits propagate to the server.
+    """
     config = await get_caldav_config(user_id)
     _check_config(config)
     tz = timezone or config.get("caldav_timezone") or None
@@ -382,6 +400,18 @@ async def update_event(
             if "LOCATION" in component:
                 del component["LOCATION"]
             component.add("location", location)
+        if recurrence is not _RECURRENCE_UNSET:
+            # Authoritatively sync the RRULE to the local event: drop the old
+            # rule, then re-add if a non-empty rule was provided (else clear it).
+            if "RRULE" in component:
+                del component["RRULE"]
+            if recurrence:
+                rrule_parts = {}
+                for part in str(recurrence).split(";"):
+                    if "=" in part:
+                        key, value = part.split("=", 1)
+                        rrule_parts[key.strip().lower()] = value.strip()
+                component.add("rrule", rrule_parts)
 
         # Rebuild ical data and save
         cal_data = icalendar.Calendar()