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

trader/auto_trader.go

@@ -206,6 +206,16 @@ func NewAutoTrader(config AutoTraderConfig, st *store.Store, userID string) (*Au
 		mcpClient.SetAPIKey(config.CustomAPIKey, config.CustomAPIURL, config.CustomModelName)
 		logger.Infof("🤖 [%s] Using MiniMax AI", config.Name)
 
+	case "blockrun-base":
+		mcpClient = mcp.NewBlockRunBaseClient()
+		mcpClient.SetAPIKey(config.CustomAPIKey, "", config.CustomModelName)
+		logger.Infof("🤖 [%s] Using BlockRun (Base Wallet) AI", config.Name)
+
+	case "blockrun-sol":
+		mcpClient = mcp.NewBlockRunSolClient()
+		mcpClient.SetAPIKey(config.CustomAPIKey, "", config.CustomModelName)
+		logger.Infof("🤖 [%s] Using BlockRun (Solana Wallet) AI", config.Name)
+
 	case "qwen":
 		mcpClient = mcp.NewQwenClient()
 		apiKey := config.QwenKey