BUG: Current Position field on Portfolio is incomplete

[pollygee]

The current_position field in the portfolios table exists and is queried in some places, but it's never updated with current portfolio values. This creates inconsistencies where classroom statistics may show outdated or incorrect portfolio totals, while the actual portfolio displays use real-time calculated values.

Where It's Used

1. ClassroomsController (line 106): Sums portfolios.current_position for classroom statistics
2. Admin Dashboard: Likely displayed in portfolio dashboard views

Fix

• Remove the field from database
• Update classroom statistics to calculate on-the-fly
• Update admin dashboard to use calculated values

We might experience a slight performance impact for classroom stats queries if that becomes a problem in the future we will address it then