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

main.go

@@ -10,6 +10,8 @@ import (
 	"nofx/logger"
 	"nofx/manager"
 	"nofx/mcp"
+	_ "nofx/mcp/payment"
+	_ "nofx/mcp/provider"
 	"nofx/store"
 	"nofx/telegram"
 	"os"
@@ -168,7 +170,7 @@ func newSharedMCPClient() mcp.AIClient {
 		logger.Warn("⚠️ DEEPSEEK_API_KEY not set, AI features will be unavailable")
 		return nil
 	}
-	return mcp.NewDeepSeekClient()
+	return mcp.NewAIClientByProvider("deepseek")
 }
 
 // initInstallationID initializes the anonymous installation ID for experience improvement