feat: add EditEventScreen with calendar and chat mode support

Add a unified event editor that works in two modes:
- Calendar mode: Create/edit events directly via EventService API
- Chat mode: Edit AI-proposed events before confirming them

The chat mode allows users to modify proposed events (title, time,
recurrence) and persists changes both locally and to the server.

New components: DateTimePicker, ScrollableDropdown, useDropdownPosition
New API: PUT /api/chat/messages/:messageId/proposal

apps/server/src/ai/utils/toolDefinitions.ts

@@ -94,10 +94,6 @@ export const TOOL_DEFINITIONS: ToolDefinition[] = [
           type: "string",
           description: "Optional event description",
         },
-        isRecurring: {
-          type: "boolean",
-          description: "Whether this is a recurring event",
-        },
         recurrenceRule: {
           type: "string",
           description: "RRULE format string for recurring events",
@@ -133,10 +129,6 @@ export const TOOL_DEFINITIONS: ToolDefinition[] = [
           type: "string",
           description: "New description (optional). NEVER put RRULE here!",
         },
-        isRecurring: {
-          type: "boolean",
-          description: "Whether this is a recurring event (optional)",
-        },
         recurrenceRule: {
           type: "string",
           description: