fix: correct clone URL, remove stale ngrok reference, and align explorer URL

- README: update clone URL from akelani-circle/fintech-starter to
  circlefin/arc-fintech and remove dangling ngrok instruction that
  referenced a non-existent step
- gateway-sdk.ts: replace unreachable explorer.arc.testnet.circle.com
  with testnet.arcscan.app to match block-explorers.ts

Author: skyc1e

README.md

@@ -24,8 +24,8 @@ Modern multi-chain treasury management system. This sample application uses Next
 1. Clone the repository and install dependencies:
 
    ```bash
-   git clone git@github.com:akelani-circle/fintech-starter.git
-   cd fintech-starter
+   git clone git@github.com:circlefin/arc-fintech.git
+   cd arc-fintech
    npm install
    ```
 
@@ -34,7 +34,6 @@ Modern multi-chain treasury management system. This sample application uses Next
    ```bash
    cp .env.example .env.local
    ```
-   Replace `your-ngrok-url` with your actual ngrok forwarding URL from step 4.
 
    Then edit `.env.local` and fill in all required values (see [Environment Variables](#environment-variables) section below).
 

lib/circle/gateway-sdk.ts

@@ -49,7 +49,7 @@ export const arcTestnet = {
     default: { http: [`https://rpc.testnet.arc.network/${arcRpcKey}`] },
   },
   blockExplorers: {
-    default: { name: 'Explorer', url: 'https://explorer.arc.testnet.circle.com' },
+    default: { name: 'Explorer', url: 'https://testnet.arcscan.app' },
   },
   testnet: true,
 } as const satisfies Chain;