Add liquidation risk simulation CLI for Sovryn

[Baliram77]

This PR adds a new risk command group for liquidation stress testing:

• rsk-cli risk simulate --shock : run Sovryn v1 liquidation simulations under price shocks
• rsk-cli risk sandbox --ltv --threshold : compare default vs custom risk parameters
• rsk-cli risk report --format json|table: structured stress-test output (CI/CD friendly)

Implementation details:

• New risk engine under src/services/risk/ (types, data sources, engine, reporting).
• Sovryn v1 positions fetched from the public subgraph, mapped into BorrowPosition and priced via CoinGecko.
• Logging and spinners use the existing logger and spinner utilities with isExternal flag, so the feature is safe to use both in the CLI and MCP server.
• README updated with a “Liquidation Risk (Stress Testing)” section and example usage.

Testing

• npm run build
• node dist/bin/index.js risk simulate --shock 40
• node dist/bin/index.js risk sandbox --ltv 65 --threshold 80
• rsk-cli risk simulate --shock 40 --asset rbtc (if this isin't work run this first npm link)
• node dist/bin/index.js risk report --format json (may occasionally hit CoinGecko 429 rate limits)

[Baliram77]

Thanks for the review — I pushed a follow-up commit (4dc54b9) addressing all findings:

• Normalized Sovryn amounts with decimals handling (wei/decimal-safe).
• Fixed stablecoin pricing (usd treated as $1; XUSD/DOC map to usd, no invalid CoinGecko id).
• Added timeouts to CoinGecko + subgraph calls and routed live paths through the timeout-aware helper.
• Unified liquidation eligibility logic and removed the 5-step cap undercount issue.
• Added input validation (NaN rejection, enforce 0 < shock < 100).
• Implemented insolvency threshold estimation via binary search.
• Added Sovryn pagination beyond 1000 results.
• Extracted formatNumber to src/utils/format.ts.
• Removed // comments in the risk-related files.
• Tested: npm run build, risk simulate, risk sandbox, risk report.