refactor: improve AI event handling and conflict display in chat

- AI fetches events on-demand via callbacks for better efficiency
- Add conflict detection with warning display when proposing overlapping events
- Improve event search and display in chat interface
- Load full chat history for display while limiting AI context

packages/shared/src/models/ChatMessage.ts

@@ -10,6 +10,12 @@ export type EventAction = "create" | "update" | "delete";
 
 export type RespondedAction = "confirm" | "reject";
 
+export interface ConflictingEvent {
+  title: string;
+  startTime: Date;
+  endTime: Date;
+}
+
 export interface ProposedEventChange {
   id: string; // Unique ID for each proposal
   action: EventAction;
@@ -19,6 +25,7 @@ export interface ProposedEventChange {
   respondedAction?: RespondedAction; // User's response to this specific proposal
   deleteMode?: RecurringDeleteMode; // For recurring event deletion
   occurrenceDate?: string; // ISO date string of specific occurrence for single/future delete
+  conflictingEvents?: ConflictingEvent[]; // Overlapping events for conflict warnings
 }
 
 export interface ChatMessage {