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/components/common/ModelIcons.tsx

@@ -14,8 +14,6 @@ const MODEL_COLORS: Record<string, string> = {
   grok: '#000000',
   openai: '#10A37F',
   minimax: '#E45735',
-  'blockrun-base': '#2563EB',
-  'blockrun-sol': '#9945FF',
   claw402: '#7C3AED',
 }
 
@@ -51,10 +49,6 @@ export const getModelIcon = (modelType: string, props: IconProps = {}) => {
     case 'minimax':
       iconPath = '/icons/minimax.svg'
       break
-    case 'blockrun-base':
-    case 'blockrun-sol':
-      iconPath = '/icons/blockrun.svg'
-      break
     case 'claw402':
       iconPath = '/icons/claw402.png'
       break