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

docs.json

@@ -44,7 +44,8 @@
           {
             "group": "Overview",
             "pages": [
-              "api-reference/introduction"
+              "api-reference/introduction",
+              "api-reference/health"
             ]
           },
           {
@@ -56,11 +57,33 @@
               "api-reference/timeframe"
             ]
           },
+          {
+            "group": "Symbols",
+            "pages": [
+              "api-reference/symbols",
+              "api-reference/symbols-summary",
+              "api-reference/symbol-details"
+            ]
+          },
+          {
+            "group": "Calendar",
+            "pages": [
+              "api-reference/calendar"
+            ]
+          },
           {
             "group": "Portfolio",
             "pages": [
               "api-reference/portfolio-holdings",
-              "api-reference/portfolio-refresh"
+              "api-reference/portfolio-refresh",
+              "api-reference/portfolio-additional"
+            ]
+          },
+          {
+            "group": "Data Import",
+            "pages": [
+              "api-reference/upload-csv",
+              "api-reference/upload-history"
             ]
           },
           {