Add investor portfolio page showing held tokens and balances

[Prasiejames]

Description

Investors need a dedicated portfolio page where they can see all the tokens they hold, their balances, current value, and yield earned.

Requirements

• New route: /portfolio
• Fetch the connected wallet's token balances from all registered RWA token contracts
• Display: token name, symbol, balance, current price, total value, yield earned (from distribution events)
• Show a summary card: total portfolio value, total yield earned, number of tokens held
• Add to sidebar navigation for "Investor" role users
• Must work with the mock data layer AND the real contract layer

Relevant files

• src/pages/portfolio.tsx (new)
• src/App.tsx (add route)
• src/components/layout/sidebar.tsx (add nav item)

Complexity: High (200 pts)

Requires building a new page, aggregating data from multiple contract sources, and handling both mock and real data paths.