Add Foreign Exchange market support for Live Trade Bench

[Ender-600]

📑 Description

• Complete forex market pipeline: Yahoo-based fetcher, dedicated agent/account/system, scheduler wiring, and extended news/social/api plumbing so FX data is generated and exposed via /api/*.
• Expand the React app (navigation, leaderboards, dashboards, news & social views, shared styles) to surface forex performance next to stock/Polymarket/BitMEX.
• Add tests/test_forex_fetcher.py covering the new fetcher’s key behaviors.

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✅ Checks

• My pull request adheres to the code style of this project
• My code requires changes to the documentation
• I have updated the documentation as required
• All the tests have passed (run pytest and frontend tests in your environment)
• Branch name follows type/descript (e.g. feature/add-forex-market)
• Ready for code review

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ℹ Additional Information

• Forex data relies on yfinance (Yahoo Finance symbols such as EURUSD=X); ensure scheduler runs once to populate models_data.json.
• New API endpoints: /api/news/forex, /api/social/forex, plus extended /api/models/ payload including "category": "forex".