Refactor SessionTracker and SessionManager into a single class

[bhouston]

Description

Currently, there seems to be both a SessionTracker and a SessionManager with overlapping responsibilities, causing confusion.

Tasks

1. Merge SessionTracker and SessionManager into a single SessionTracker class

   • Move appropriate SessionManager functionality into SessionTracker
   • Convert standalone functions from SessionManager (like session starting or browser detection) into helper functions

2. Refactor BrowserDetector to use a functional approach

   • Convert the class-based implementation to standalone functions
   • Remove the class container which doesn't provide significant benefits

Goal

Simplify the codebase by eliminating redundant abstractions and improving code organization.

Acceptance Criteria

• All existing functionality is preserved
• Tests pass after refactoring
• Code is cleaner and responsibilities are clearer