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>

pkg/arbitrum/connection.go

@@ -223,7 +223,6 @@ func (cm *ConnectionManager) getFallbackEndpoints() []string {
 	if len(endpoints) == 0 {
 		endpoints = []string{
 			"https://arb1.arbitrum.io/rpc",
-			"https://arbitrum.llamarpc.com",
 			"https://arbitrum-one.publicnode.com",
 			"https://arbitrum-one.public.blastapi.io",
 		}