feat: add video conference meeting link generation to event modal

- Add video conference utility functions for generating random meeting IDs
- Implement video meeting button with camera icon in EventModal
- Add copy and delete functionality with IconButton components
- Support X-OPENPAAS-VIDEOCONFERENCE field in CalendarEvent type
- Handle state management for editing events with/without video conference
- Add meeting link footer to event description
- Include comprehensive test suite for video conference utilities

Features:
- Generate random meeting links (format: xxx-xxxx-xxx)
- Copy meeting link to clipboard
- Remove video conference from events
- Proper state sync when editing different events
- Integration with existing JCal/ICS conversion

src/utils/videoConferenceUtils.ts

@@ -0,0 +1,48 @@
+/**
+ * Utility functions for video conference meeting generation
+ */
+
+/**
+ * Generate a random meeting ID in format xxx-xxxx-xxx
+ * @returns {string} Random meeting ID
+ */
+export function generateMeetingId(): string {
+  const chars = 'abcdefghijklmnopqrstuvwxyz';
+  const generateSegment = (length: number): string => {
+    return Array.from({ length }, () => chars[Math.floor(Math.random() * chars.length)]).join('');
+  };
+  
+  return `${generateSegment(3)}-${generateSegment(4)}-${generateSegment(3)}`;
+}
+
+/**
+ * Generate a complete meeting link
+ * @param {string} baseUrl - Base URL for video conference (from .env.js)
+ * @returns {string} Complete meeting link
+ */
+export function generateMeetingLink(baseUrl?: string): string {
+  const base = baseUrl || (window as any).VIDEO_CONFERENCE_BASE_URL || 'https://meet.linagora.com';
+  const meetingId = generateMeetingId();
+  return `${base}/${meetingId}`;
+}
+
+/**
+ * Add video conference footer to event description
+ * @param {string} description - Original description
+ * @param {string} meetingLink - Generated meeting link
+ * @returns {string} Description with video conference footer
+ */
+export function addVideoConferenceToDescription(description: string, meetingLink: string): string {
+  const footer = `\n\nVisio: ${meetingLink}`;
+  return description + footer;
+}
+
+/**
+ * Extract video conference link from description
+ * @param {string} description - Event description
+ * @returns {string | null} Video conference link if found, null otherwise
+ */
+export function extractVideoConferenceFromDescription(description: string): string | null {
+  const match = description.match(/Visio:\s*(https?:\/\/[^\s]+)/);
+  return match ? match[1] : null;
+}