refactor: extract shared EventCardBase component

- Create EventCardBase with common layout, icons (calendar, clock, repeat), and formatting functions
- Refactor EventCard and ProposedEventCard to use EventCardBase
- Add event details to delete action responses for better UX
- Include event title in delete confirmation message

CLAUDE.md

@@ -77,9 +77,10 @@ src/
 ├── components/
 │   ├── BaseBackground.tsx      # Common screen wrapper
 │   ├── Header.tsx              # Header component
-│   ├── EventCard.tsx           # Event card for calendar display
+│   ├── EventCardBase.tsx       # Shared event card layout with icons (used by EventCard & ProposedEventCard)
+│   ├── EventCard.tsx           # Calendar event card (uses EventCardBase + edit/delete buttons)
 │   ├── EventConfirmDialog.tsx  # AI-proposed event confirmation modal
-│   └── ProposedEventCard.tsx   # Inline event proposal with confirm/reject buttons
+│   └── ProposedEventCard.tsx   # Chat event proposal (uses EventCardBase + confirm/reject buttons)
 ├── Themes.tsx                  # Centralized color/theme definitions
 ├── services/
 │   ├── index.ts                # Re-exports all services
@@ -305,8 +306,9 @@ MONGODB_URI=mongodb://root:mongoose@localhost:27017/calchat?authSource=admin
 - `ApiClient`: get(), post(), put(), delete() implemented
 - `EventService`: getAll(), getById(), getByDateRange(), create(), update(), delete() - fully implemented
 - `ChatService`: sendMessage(), confirmEvent(convId, msgId, action, event?, eventId?, updates?), rejectEvent() - supports create/update/delete actions
-- `EventCard`: Displays event details (title, date, time, duration, recurring indicator) with Feather icons and edit/delete buttons
-- `ProposedEventCard`: Displays proposed events (title, date, description, recurring indicator) with confirm/reject buttons
+- `EventCardBase`: Shared base component with event layout (header, date/time/recurring icons, description) - used by both EventCard and ProposedEventCard
+- `EventCard`: Uses EventCardBase + edit/delete buttons for calendar display
+- `ProposedEventCard`: Uses EventCardBase + confirm/reject buttons for chat proposals (supports create/update/delete actions)
 - `Themes.tsx`: Centralized color definitions including textPrimary, borderPrimary, eventIndicator
 - `EventsStore`: Zustand store with setEvents(), addEvent(), updateEvent(), deleteEvent() - stores ExpandedEvent[]
 - `ChatStore`: Zustand store with addMessage(), updateMessage(), clearMessages() - persists messages across tab switches