fix: improve video conference link positioning and null safety

- Fix calendarUtils.ts null safety for calendars[id] access
- Update video conference link to be added on line 2 instead of line 3
- Update regex in handleDeleteVideoConference to match new format
- Update all test cases for videoConferenceUtils to match new format
- Add null checks in updateCalsDetails function

src/utils/videoConferenceUtils.ts

@@ -42,7 +42,7 @@ export function addVideoConferenceToDescription(
   description: string,
   meetingLink: string
 ): string {
-  const footer = `\n\nVisio: ${meetingLink}`;
+  const footer = `\nVisio: ${meetingLink}`;
   return description + footer;
 }