Add "Sell Stock" Functionality

[13Sharad]

Description: Implement the "Sell Stock" feature, enabling users to sell stocks directly from the NexTrade platform for greater control over their investments.

Acceptance Criteria:

Users can select a stock to sell from their portfolio.
Required form fields:
Stock name
Quantity to sell
Display a confirmation prompt before finalizing the sale.
Show a success message upon completion.
Additional Notes:

Ensure compatibility with the existing wallet connection.
Implement error handling for insufficient shares.