feat: bridge waits for confirmation, tx retry, better errors

[starc007]

Summary

• Bridge now waits — polls /intents/status/v2 after tx submit until success, failure, or refund (120s timeout with fallback command shown)
• TX retry — retries failed sends up to 2 times, re-fetching nonce each attempt to handle conflicts
• Actionable error messages — insufficient funds, rejected tx, RPC connection failures all surface clear next steps
• No private key — shows all 3 ways to set it instead of generic env var error
• Quote failures — surfaces HTTP status + API error body directly

Test plan

• relay bridge from Base → Arbitrum completes and prints bridge confirmed ✓
• Bridge with insufficient funds shows clear error
• Bridge with no private key set shows all 3 configuration options
• Quote with invalid token shows API error message