refactor: restructure project directories for better modularity

- Delete llm/ dead code (3 files, zero references)
- Split mcp/ into sub-packages: mcp/provider/ (8 providers) and
  mcp/payment/ (4 payment clients) with registry pattern
- Export Client internal fields and ClientHooks interface for
  sub-package access
- Split api/server.go (3892 lines) into 8 domain-specific handler files
- Split trader/auto_trader.go (2296 lines) into 5 focused files
- Reorganize web/src/components/ flat files into auth/, charts/,
  trader/, common/, modals/, backtest/ subdirectories
- Update all consumer imports to use registry-based provider creation

web/src/pages/PageNotFound.tsx

@@ -1,4 +1,4 @@
-import { DeepVoidBackground } from '../components/DeepVoidBackground'
+import { DeepVoidBackground } from '../components/common/DeepVoidBackground'
 import { AlertCircle, Home } from 'lucide-react'
 
 export function PageNotFound() {