Remove task sharing references from documentation

Task sharing is not currently implemented and removed:
- Task Sharing feature from User Management section
- Shared Views feature description
- TaskShare database model documentation
- Updated description to remove "real-time collaboration"

The application currently supports multi-user authentication and
user management, but does not include task sharing functionality.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

README.md

@@ -1,6 +1,6 @@
 # KeepItGoing Server
 
-A powerful Django-based task management system with time tracking, tag organization, and real-time collaboration features.
+A powerful Django-based task management system with time tracking, tag organization, and multi-user support.
 
 ## Features
 
@@ -23,14 +23,12 @@ A powerful Django-based task management system with time tracking, tag organizat
 - **Formatted Display**: Time shown as H:MM:SS with visual indicators
 - **Running Timer Display**: Always visible timer in the UI when tracking time
 
-### Collaboration & User Management
+### User Management
-- **Task Sharing**: Share individual tasks or entire tags with other users
 - **Multi-user Support**: Full authentication and user management
 - **Email Verification**: Secure email verification for new user registrations
 - **Admin Approval**: Optional admin approval workflow for new users
 - **User Profiles**: Customizable profiles with timezone and notification preferences
 - **Password Management**: Secure password change functionality
-- **Shared Views**: See tasks shared with you alongside your own
 
 ### User Interface
 - **3-Pane Layout**: Sidebar navigation, task list, and detail panel
@@ -535,11 +533,6 @@ docker-compose up -d
 - Duration calculation
 - User association
 
-### TaskShare
-- Share tasks or entire tags
-- User-to-user sharing
-- Permission management
-
 ## Development
 
 ### Running Tests