refactor: remove BlockRun provider, retain Claw402 as sole x402 payment provider

Remove all BlockRun (Base + Solana wallet) references from codebase:
- Delete blockrun_base.go, blockrun_sol.go, wallet setup docs, icon
- Move shared EIP-712 signing code to x402.go for Claw402 reuse
- Clean up provider constants, model lists, UI components, translations
- Update all README files (EN + 6 i18n) and getting-started docs

web/src/i18n/translations.ts

@@ -1224,7 +1224,6 @@ export const translations = {
       fundStep3: '$5-10 USDC lasts a long time (~$0.003/call)',
       back: 'Back',
       startTrading: 'Start Trading',
-      viaBlockrunWallet: 'Via BlockRun Wallet',
       modelsConfigured: 'Models with gold badge are already configured',
       getStarted: 'Get Started',
       getApiKey: 'Get API Key',
@@ -2513,7 +2512,6 @@ export const translations = {
       fundStep3: '充入 $5-10 USDC 即可使用很长时间（约 $0.003/次调用）',
       back: '返回',
       startTrading: '开始交易',
-      viaBlockrunWallet: '通过钱包支付',
       modelsConfigured: '带金色标记的模型已配置',
       getStarted: '开始使用',
       getApiKey: '获取 API Key',
@@ -3607,7 +3605,6 @@ export const translations = {
       fundStep3: '$5-10 USDC cukup untuk waktu lama (~$0.003/panggilan)',
       back: 'Kembali',
       startTrading: 'Mulai Trading',
-      viaBlockrunWallet: 'Via BlockRun Wallet',
       modelsConfigured: 'Model dengan lencana emas sudah dikonfigurasi',
       getStarted: 'Mulai',
       getApiKey: 'Dapatkan API Key',