fix: Settings now correctly displays CalDAV integrations when more than one isconfigured (#2901)

* fix(calendar): expose source in calendar list and add per-calendar delete

- GET /api/calendar/calendars now includes source field so the frontend
  can distinguish CalDAV collections from local calendars
- Add DELETE /api/calendar/calendars/{cal_id} to remove a specific
  calendar and its events by owner-scoped ID

* fix(settings): show all CalDAV calendars in integrations list

Previously one card was shown for the CalDAV server connection regardless
of how many calendar collections had been synced. The Calendars page showed
them all; Settings did not.

- Fetch /api/calendar/calendars alongside existing requests and render
  one card per source=caldav collection, falling back to the single
  server-level card if nothing has synced yet
- Delete now targets the specific calendar by ID rather than clearing
  the whole server config
- Confirm dialog shows the calendar name so the user can verify before
  removing

routes/calendar_routes.py

@@ -729,6 +729,28 @@ def setup_calendar_routes() -> APIRouter:
         from src.caldav_sync import sync_caldav
         return await sync_caldav(owner)
 
+    @router.delete("/calendars/{cal_id}")
+    async def delete_calendar(cal_id: str, request: Request):
+        owner = _require_user(request)
+        db = SessionLocal()
+        try:
+            cal = db.query(CalendarCal).filter(
+                CalendarCal.id == cal_id,
+                CalendarCal.owner == owner,
+            ).first()
+            if not cal:
+                raise HTTPException(404, "Calendar not found")
+            db.delete(cal)
+            db.commit()
+            return {"ok": True}
+        except HTTPException:
+            raise
+        except Exception as e:
+            logger.error("Failed to delete calendar %s: %s", cal_id, e)
+            raise HTTPException(500, "Failed to delete calendar")
+        finally:
+            db.close()
+
     @router.get("/calendars")
     async def list_calendars(request: Request):
         owner = _require_user(request)
@@ -737,7 +759,7 @@ def setup_calendar_routes() -> APIRouter:
             _ensure_default_calendar(db, owner)
             cals = db.query(CalendarCal).filter(CalendarCal.owner == owner).all()
             return {"calendars": [
-                {"name": c.name, "href": c.id, "color": c.color}
+                {"name": c.name, "href": c.id, "color": c.color, "source": c.source}
                 for c in cals
             ]}
         except HTTPException: