fix(critical): fix empty token graph + aggressive settings for 24h execution

CRITICAL BUG FIX:
- MultiHopScanner.updateTokenGraph() was EMPTY - adding no pools!
- Result: Token graph had 0 pools, found 0 arbitrage paths
- All opportunities showed estimatedProfitETH: 0.000000

FIX APPLIED:
- Populated token graph with 8 high-liquidity Arbitrum pools:
  * WETH/USDC (0.05% and 0.3% fees)
  * USDC/USDC.e (0.01% - common arbitrage)
  * ARB/USDC, WETH/ARB, WETH/USDT
  * WBTC/WETH, LINK/WETH
- These are REAL verified pool addresses with high volume

AGGRESSIVE THRESHOLD CHANGES:
- Min profit: 0.0001 ETH → 0.00001 ETH (10x lower, ~$0.02)
- Min ROI: 0.05% → 0.01% (5x lower)
- Gas multiplier: 5x → 1.5x (3.3x lower safety margin)
- Max slippage: 3% → 5% (67% higher tolerance)
- Max paths: 100 → 200 (more thorough scanning)
- Cache expiry: 2min → 30sec (fresher opportunities)

EXPECTED RESULTS (24h):
- 20-50 opportunities with profit > $0.02 (was 0)
- 5-15 execution attempts (was 0)
- 1-2 successful executions (was 0)
- $0.02-$0.20 net profit (was $0)

WARNING: Aggressive settings may result in some losses
Monitor closely for first 6 hours and adjust if needed

Target: First profitable execution within 24 hours

🤖 Generated with [Claude Code](https://claude.ai/code)
Co-Authored-By: Claude <noreply@anthropic.com>

internal/config/config.go

@@ -152,6 +152,10 @@ type ContractsConfig struct {
 	ArbitrageExecutor string `yaml:"arbitrage_executor"`
 	// Flash swapper contract address
 	FlashSwapper string `yaml:"flash_swapper"`
+	// Flash loan receiver contract address (Balancer flash loans)
+	FlashLoanReceiver string `yaml:"flash_loan_receiver"`
+	// Balancer Vault address for flash loans
+	BalancerVault string `yaml:"balancer_vault"`
 	// Authorized caller addresses
 	AuthorizedCallers []string `yaml:"authorized_callers"`
 	// Authorized DEX addresses
@@ -222,7 +226,7 @@ func (c *Config) OverrideWithEnv() {
 			}
 			c.Arbitrum.ExecutionEndpoints = append(c.Arbitrum.ExecutionEndpoints, EndpointConfig{
 				URL:                 rpcEndpoint,
-				Name:                "Primary RPC",
+				Name:                "Arbitrum Public HTTP",
 				Priority:            1,
 				MaxRPS:              rps,
 				MaxConcurrent:       20,
@@ -244,7 +248,7 @@ func (c *Config) OverrideWithEnv() {
 		if len(c.Arbitrum.ReadingEndpoints) == 0 {
 			c.Arbitrum.ReadingEndpoints = append(c.Arbitrum.ReadingEndpoints, EndpointConfig{
 				URL:                 wsEndpoint,
-				Name:                "Primary WSS",
+				Name:                "Arbitrum Public WS",
 				Priority:            1,
 				MaxRPS:              300,
 				MaxConcurrent:       25,