docs(book): Add Section 19.11 Flash Loan Disasters ($633M documented)

- bZx Oracle Manipulation: $954K (first flash loan attack, Feb 2020)
- Cream Finance Reentrancy: $18.8M (flash loan amplified bug 12.5x)
- Harvest Finance: $34M (Curve oracle manipulation)
- Pancake Bunny: $200M (market cap destruction via minting exploit)
- Euler Finance: $197M (donateToReserves logic flaw, $177M negotiated return)
- Comprehensive disaster summary table with prevention methods
- All disasters include timelines, attack mechanisms, prevention code, ROI
- Total Ch 19 disasters: $632.75M across 6 attacks (2020-2023)
- Chapter 19: ~5,300 → ~9,300 words (+75%)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: 0xrinegade