feat: Add contract security verification before transaction signing

### Describe the solution you'd like

## Problem

Users interacting with dApps built on OnchainKit have zero visibility
into contract safety before signing a transaction. There is currently
no way to know if a contract is verified, is a proxy, or presents
any risk signals.

## Proposed Solution

Add a `` component that automatically analyzes
contract addresses from `TransactionContext` and displays risk
indicators before the user signs.

```tsx

```

Shows:
- ✅ Contract verified
- ⚠️ Proxy contract (with implementation address)
- 🔴 Contract not verified

## Implementation

PR #2636 implements this feature as a standalone component
with no dependency on other open PRs.

## Describe alternatives you've considered

**Revoke.cash / existing allowance managers** — standalone tools
that users must visit separately. Not integrated into the transaction
flow where the risk actually occurs.

**Manual implementation per dApp** — each team builds their own
contract verification check. Inconsistent, unaudited, duplicated effort.

OnchainKit's SecurityCheck solves this at the framework level —
one implementation, consistent UX across all dApps built with OnchainKit.