feat: add SharePoint integration with session validation and UI components

[abfeb8]

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)

  • New Components
    • Added SharePointPicker.tsx component for connecting to and selecting files from SharePoint
    • Created reusable components:
      • ConnectedStateSkeleton.tsx - loading state for connection status
      • FileSelectionSkeleton.tsx - loading state for file selection interface
  • Utility Improvements
    • Added validateProviderSession function to standardize session validation across providers
    • Refactored GoogleDrivePicker to use this new utility function
  • UI Updates
    • Added SharePoint SVG icon
    • Modified ConnectorAuth component to better handle longer email addresses
    • Updated the Upload component to support SharePoint as a document source
  • Configuration
    • Added SharePoint as a new ingestor type with appropriate form schema
    • Created default configuration for the SharePoint ingestor
  • Localization
    • Added SharePoint-related translations to all language files (en, es, jp, ru, zh-TW, zh)

• Why was this change needed? (You can also link to an open issue here)

  • Auth flow UI implementation for Sharepoint ingestion arc53/DocsGPT#1180

• Other information:

  • Follow-up of PR feat: add Microsoft Entra ID integration arc53/DocsGPT#2029