feat: Add calendar UI with place/time context integration

CALENDAR_ENHANCEMENT.md

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+# Calendar UI Enhancement with Place/Time Context
+
+## Overview
+
+This enhancement adds comprehensive place and time context management to the QCX calendar system, integrating with Mapbox MCP to provide structured location and temporal information.
+
+## Features
+
+### 1. Enhanced Time Management
+- **Time Picker**: Select specific time (HH:MM:SS) for calendar notes
+- **Timezone Support**: Choose from 20+ common timezones
+- **Auto-detection**: Automatically detects user's current timezone
+
+### 2. Location Tagging with Mapbox MCP
+- **Map Integration**: Tag notes with current map position
+- **Geocoding**: Automatically fetches place names using Mapbox MCP
+- **Visual Feedback**: Shows tagged coordinates in real-time
+
+### 3. Structured Context Format
+All location-tagged notes display context in the standardized format:
+```
+latitude, longitude TIME (HH:MM:SS): DD/MM/YYYY Timezone
+```
+
+Example:
+```
+40.758896, -73.985130 TIME (14:30:45): 20/11/2025 America/New_York
+```
+
+## Implementation Details
+
+### Database Schema Changes
+
+Added `timezone` field to `calendar_notes` table:
+```sql
+ALTER TABLE calendar_notes ADD COLUMN timezone VARCHAR(100);
+```
+
+### New Components
+
+1. **CalendarNotepadEnhanced** (`components/calendar-notepad-enhanced.tsx`)
+   - Enhanced version of the calendar notepad
+   - Includes time and timezone selectors
+   - Integrates with Mapbox MCP for geocoding
+
+2. **Calendar Context Utilities** (`lib/utils/calendar-context.ts`)
+   - `formatPlaceTimeContext()`: Formats notes into standardized context string
+   - `parsePlaceTimeContext()`: Parses context strings back into components
+   - `createGeoJSONPoint()`: Creates GeoJSON Point objects
+   - `getCurrentTimezone()`: Gets user's current timezone
+   - `COMMON_TIMEZONES`: List of 20+ common timezones
+
+### Updated Files
+
+- `lib/db/schema.ts`: Added timezone field
+- `lib/types/index.ts`: Updated CalendarNote type
+- `components/chat.tsx`: Switched to CalendarNotepadEnhanced
+- `drizzle/migrations/0002_add_timezone_to_calendar_notes.sql`: Migration file
+
+## Usage
+
+### Creating a Note with Location and Time
+
+1. Open the calendar view in QCX
+2. Select the desired date from the date picker
+3. Set the time using the time picker (defaults to current time)
+4. Select the appropriate timezone
+5. Navigate the map to your desired location
+6. Click the MapPin icon to tag the location
+7. Type your note content
+8. Press Cmd+Enter (Mac) or Ctrl+Enter (Windows) to save
+
+### Viewing Notes
+
+Notes with location tags display:
+- The note content
+- A formatted context string with coordinates, time, date, and timezone
+- A MapPin button to fly to the location on the map
+
+### Mapbox MCP Integration
+
+The calendar automatically integrates with Mapbox MCP when available:
+- **Connected**: Automatically geocodes coordinates to place names
+- **Disconnected**: Falls back to simple coordinate tagging
+
+## API
+
+### formatPlaceTimeContext(note: CalendarNote): string
+
+Formats a calendar note into the standardized context string.
+
+**Parameters:**
+- `note`: CalendarNote object with locationTags
+
+**Returns:**
+- Formatted string: `"lat, lng TIME (HH:MM:SS): DD/MM/YYYY Timezone"`
+- Empty string if no location tags
+
+### parsePlaceTimeContext(contextString: string): object | null
+
+Parses a context string back into components.
+
+**Parameters:**
+- `contextString`: Formatted context string
+
+**Returns:**
+```typescript
+{
+  latitude: number
+  longitude: number
+  time: string        // HH:MM:SS
+  date: string        // DD/MM/YYYY
+  timezone: string
+}
+```
+
+## Supported Timezones
+
+The system supports 20+ common timezones including:
+- UTC
+- Americas: New York, Chicago, Denver, Los Angeles, Toronto, Mexico City, São Paulo
+- Europe: London, Paris, Berlin, Moscow
+- Asia: Dubai, Kolkata, Shanghai, Tokyo, Seoul, Singapore
+- Oceania: Sydney, Auckland
+
+## Migration
+
+To apply the database changes:
+
+```bash
+bun run db:migrate
+```
+
+Or manually run the migration:
+```bash
+psql -d your_database -f drizzle/migrations/0002_add_timezone_to_calendar_notes.sql
+```
+
+## Testing
+
+The enhanced calendar can be tested by:
+1. Creating notes with different times and timezones
+2. Tagging locations from the map
+3. Verifying the context string format
+4. Flying to tagged locations
+5. Testing with and without Mapbox MCP connection
+
+## Future Enhancements
+
+Potential improvements:
+- Recurring events support
+- Calendar export (iCal format)
+- Time range queries
+- Timezone conversion display
+- Location-based note search
+- Integration with external calendar services
+
+## Dependencies
+
+- Mapbox MCP server (optional, for enhanced geocoding)
+- Mapbox GL JS (for map integration)
+- Lucide React (for icons)
+- Drizzle ORM (for database)
+
+## Compatibility
+
+- Works with existing calendar notes (timezone defaults to UTC)
+- Backward compatible with original CalendarNotepad
+- Mobile and desktop responsive