feat: add BlockRun wallet provider for pay-per-request AI access (#1408)

Integrates BlockRun (blockrun.ai) as a new AI provider option via x402
micropayment protocol, allowing users to access top AI models with USDC
without requiring individual API keys.

- Add BlockRun Base (EVM) and Solana wallet providers to model selector
- Implement x402 v2 EIP-712 payment signing for Base (mcp/blockrun_base.go)
- Implement x402 v2 SPL TransferChecked signing for Solana (mcp/blockrun_sol.go)
- Wire blockrun-base and blockrun-sol into trader factory (auto_trader.go)
- Register both providers in supported models API (server.go)
- Add BlockRun card UI with wallet key input in Step 0/1 of model config modal
- Add BlockRun SVG icon and ModelIcons support
- Add setup guides for Base and Solana wallet configuration (docs/)
- Available flagship models: GPT-5.4, Claude Opus 4.6, Gemini 3.1 Pro,
  Grok 3, DeepSeek Chat, MiniMax M2.5

docs/getting-started/blockrun-sol-wallet.md

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+# BlockRun Solana Wallet Setup Guide
+
+This guide explains how to use a Solana wallet to pay for AI usage through BlockRun — no API key required.
+
+**Language:** [English](blockrun-sol-wallet.md) | [中文](blockrun-sol-wallet.zh-CN.md)
+
+## What is BlockRun?
+
+[BlockRun](https://blockrun.ai) is a decentralized AI inference gateway that lets you access top AI models (Claude, GPT, Gemini, Grok, DeepSeek, etc.) by paying per request with USDC — no monthly subscriptions, no API key signups.
+
+NOFX integrates BlockRun via the **x402 micropayment protocol** on Solana: each AI inference request automatically pays a small USDC fee directly from your wallet.
+
+## Prerequisites
+
+- A Solana wallet with USDC on **Solana mainnet**
+- The wallet private key (base58-encoded, 64 bytes — standard Solana keypair format)
+
+### Getting USDC on Solana
+
+1. Buy SOL on any exchange and withdraw to your Solana wallet, then swap to USDC on [Jupiter](https://jup.ag), **or**
+2. Buy USDC directly on an exchange and withdraw to Solana, **or**
+3. Bridge from other chains using [Wormhole](https://wormhole.com)
+
+> **Tip:** A few dollars of USDC is plenty to start.
+
+## Step 1: Export Your Solana Private Key
+
+> ⚠️ **Security Warning:** Use a dedicated wallet for NOFX — not your main holdings wallet.
+
+**From Phantom Wallet:**
+1. Open Phantom → Settings (gear icon)
+2. Security & Privacy → Export Private Key
+3. Enter your password
+4. Copy the base58 key (looks like: `5J...` — a long string of ~88 characters)
+
+**From Solflare:**
+1. Settings → Export Private Key
+2. The key is displayed in base58 format
+
+**From CLI (solana-keygen):**
+```bash
+# View existing keypair
+cat ~/.config/solana/id.json
+# This is a JSON array — convert to base58 using:
+solana-keygen pubkey ~/.config/solana/id.json
+```
+
+> **Note:** NOFX accepts the **base58-encoded 64-byte keypair** (as exported by Phantom/Solflare). This is the standard format for Solana private keys.
+
+## Step 2: Fund the Wallet with USDC on Solana
+
+Send USDC to your Solana wallet:
+- **USDC SPL token mint:** `EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v`
+- **Network:** Solana Mainnet
+- **Recommended starting amount:** $5–$20 USDC
+
+Check your balance at [solscan.io](https://solscan.io) or in your wallet app.
+
+## Step 3: Configure in NOFX
+
+1. Open NOFX at `http://localhost:3000`
+2. Log in and go to **Config** tab
+3. Click **+ Add AI Model**
+4. In Step 0, scroll to **Via BlockRun Wallet** section
+5. Select **BlockRun · Solana Wallet**
+6. In Step 1, configure:
+   - **Wallet Private Key:** Your base58-encoded Solana private key
+   - **Select Model:** Choose from Claude Opus, GPT-5.4, Gemini 3 Pro, Grok 3, DeepSeek R1, or leave as **Auto** for best available
+7. Click **Save**
+
+## How Payment Works
+
+When NOFX sends an AI request:
+
+1. Request goes to `https://sol.blockrun.ai/api/v1/chat/completions`
+2. Server responds with HTTP `402 Payment Required` + payment details (nonce, recipient, amount)
+3. NOFX signs the payment message `blockrun-payment:{nonce}:{recipient}:{amount}` with your **Ed25519** private key
+4. Payment signature is attached and request is retried
+5. BlockRun verifies the Ed25519 signature on-chain and routes to the AI model
+
+> **Privacy:** Your private key never leaves your NOFX instance. Only the cryptographic signature is sent.
+
+## Available Models via BlockRun
+
+| Model ID | Provider | Use Case |
+|----------|----------|----------|
+| `gpt-5.4` | OpenAI | Flagship (default) |
+| `claude-opus-4.6` | Anthropic | Flagship |
+| `gemini-3.1-pro` | Google | Flagship |
+| `grok-3` | xAI | Flagship |
+| `deepseek-chat` | DeepSeek | Flagship |
+| `minimax-m2.5` | MiniMax | Flagship |
+
+## Security Best Practices
+
+- ✅ Use a **dedicated trading wallet** with only your AI budget
+- ✅ Keep only a small USDC balance (top up as needed)
+- ✅ Your private key is AES-256 encrypted at rest in NOFX's database
+- ✅ Ed25519 signatures are one-time — each authorizes only one specific payment
+- ❌ Never use your main SOL holdings wallet as the NOFX trading wallet
+
+## Troubleshooting
+
+| Issue | Solution |
+|-------|----------|
+| `unexpected key length` | Ensure you exported the full 64-byte keypair (not just the 32-byte seed) |
+| `failed to decode base58` | Key must be base58 encoded (standard Phantom/Solflare export format) |
+| `payment retry failed` | Ensure you have USDC on **Solana mainnet** (not devnet) |
+| No response from server | Check `sol.blockrun.ai` is reachable from your server |
+| Slow responses | Try selecting a specific model instead of "Auto" |
+
+## Monitoring Spend
+
+Check your USDC balance and transaction history at:
+- [Solscan](https://solscan.io) — search your wallet address, filter by USDC token
+- [BlockRun dashboard](https://blockrun.ai) — usage history
+
+---
+
+[← Back to Getting Started](README.md)