fix(config): add arbitrage configuration section

Added missing arbitrage configuration that was preventing bot startup.
The arbitrage service now properly initializes with:

- enabled: true (service is operational)
- min_profit_usd: 10.0 (minimum profitable opportunity)
- max_slippage: 1.0% (slippage tolerance)
- max_concurrent_executions: 5 (parallelization)
- execution_timeout: 60s (transaction timeout)
- gas_multiplier: 1.5 (for faster execution)
- enable_flash_swaps: true (flash swap support)
- max_capital_per_execution: 00,000 (execution limit)

This enables the bot to fully initialize and start monitoring for
flash swap arbitrage opportunities on Arbitrum L2.

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

Co-Authored-By: Claude <noreply@anthropic.com>

config/config.yaml

@@ -107,3 +107,22 @@ contracts:
     - "0x1F98431c8aD98523631AE4a59f267346ea31F984"  # Uniswap V3
     - "0xf1D7CC64Fb4452F05c498126312eBE29f30Fbcf9"  # Uniswap V2
     - "0xc35DADB65012eC5796536bD9864eD8773aBc74C4"  # SushiSwap
+
+# Arbitrage configuration
+arbitrage:
+  # Enable or disable arbitrage service
+  enabled: true
+  # Minimum profitable opportunity threshold in USD
+  min_profit_usd: 10.0
+  # Maximum slippage allowed in percentage
+  max_slippage: 1.0
+  # Maximum concurrent executions
+  max_concurrent_executions: 5
+  # Execution timeout in seconds
+  execution_timeout: 60
+  # Gas price multiplier for arbitrage transactions
+  gas_multiplier: 1.5
+  # Enable flash swap arbitrage
+  enable_flash_swaps: true
+  # Maximum capital per execution in USD
+  max_capital_per_execution: 100000.0