feat: improve video conference UI in EventModal

- Replace 'Meeting link generated' text with 'Join Visio conference' button
- Button opens video conference link in new tab when clicked
- Use contained variant styling to match Save button appearance
- Maintain copy and delete functionality for meeting links

src/components/Calendar/CalendarSelection.tsx

@@ -8,7 +8,6 @@ import { useState } from "react";
 import CalendarPopover from "./CalendarModal";
 import { Calendars } from "../../features/Calendars/CalendarTypes";
 import MoreVertIcon from "@mui/icons-material/MoreVert";
-import ArrowDropDownIcon from "@mui/icons-material/ArrowDropDown";
 import IconButton from "@mui/material/IconButton";
 import Checkbox from "@mui/material/Checkbox";
 import ExpandMoreIcon from "@mui/icons-material/ExpandMore";