Refactor API documentation:

- Removed SSO configuration section from auth.mdx
- Added new calendar.mdx for calendar data endpoints
- Introduced health.mdx for health check endpoints
- Updated introduction.mdx to include new symbols and calendar sections
- Created portfolio-additional.mdx for additional portfolio operations
- Added symbol-details.mdx for detailed symbol information
- Created symbols-summary.mdx for comprehensive symbol statistics
- Added symbols.mdx for retrieving all traded symbols
- Created upload-csv.mdx for uploading transaction history and realized gains
- Added upload-history.mdx for retrieving upload history
- Updated docs.json to reflect new and modified documentation structure

api-reference/introduction.mdx

@@ -40,15 +40,27 @@ All API endpoints require authentication via Google OAuth 2.0. The API uses sess
   <Card title="Trading Data" icon="chart-line" href="/api-reference/months">
     Access monthly trading data, P&L reports, and individual trade details
   </Card>
+  <Card title="Symbols" icon="tag" href="/api-reference/symbols">
+    Get symbol lists, trading statistics, and detailed performance data
+  </Card>
+  <Card title="Calendar" icon="calendar-days" href="/api-reference/calendar">
+    View daily trading activity, export reports, and market metrics
+  </Card>
   <Card title="Portfolio" icon="briefcase" href="/api-reference/portfolio-holdings">
     Manage portfolio holdings and trigger price updates
   </Card>
+  <Card title="Data Import" icon="upload" href="/api-reference/upload-csv">
+    Upload CSV files and view import history
+  </Card>
   <Card title="Timeframe Analysis" icon="calendar" href="/api-reference/timeframe">
     Query trading performance across custom date ranges
   </Card>
   <Card title="Authentication" icon="lock" href="/api-reference/auth">
     OAuth endpoints and session management
   </Card>
+  <Card title="Health Checks" icon="heart-pulse" href="/api-reference/health">
+    Monitor application health and readiness
+  </Card>
 </CardGroup>
 
 ## Response Format
@@ -238,15 +250,27 @@ if (!data.success) {
 ## Next Steps
 
 <CardGroup cols={2}>
+  <Card title="Health Checks" icon="heart-pulse" href="/api-reference/health">
+    Application monitoring and health endpoints
+  </Card>
   <Card title="Authentication" icon="lock" href="/api-reference/auth">
     Learn about OAuth flow and session management
   </Card>
   <Card title="Trading Data" icon="chart-line" href="/api-reference/months">
     Explore trading data endpoints
   </Card>
+  <Card title="Symbols" icon="tag" href="/api-reference/symbols">
+    Symbol lists and performance data
+  </Card>
   <Card title="Portfolio API" icon="briefcase" href="/api-reference/portfolio-holdings">
     Manage portfolio holdings
   </Card>
+  <Card title="Calendar" icon="calendar-days" href="/api-reference/calendar">
+    Daily activity and export reports
+  </Card>
+  <Card title="Data Import" icon="upload" href="/api-reference/upload-csv">
+    Upload and track CSV imports
+  </Card>
   <Card title="Timeframe Analysis" icon="calendar" href="/api-reference/timeframe">
     Query custom date ranges
   </Card>