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

mcp/provider/deepseek.go

@@ -0,0 +1,69 @@
+package provider
+
+import (
+	"net/http"
+
+	"nofx/mcp"
+)
+
+func init() {
+	mcp.RegisterProvider(mcp.ProviderDeepSeek, func(opts ...mcp.ClientOption) mcp.AIClient {
+		return NewDeepSeekClientWithOptions(opts...)
+	})
+}
+
+type DeepSeekClient struct {
+	*mcp.Client
+}
+
+func (c *DeepSeekClient) BaseClient() *mcp.Client { return c.Client }
+
+// NewDeepSeekClient creates DeepSeek client (backward compatible)
+//
+// Deprecated: Recommend using NewDeepSeekClientWithOptions for better flexibility
+func NewDeepSeekClient() mcp.AIClient {
+	return NewDeepSeekClientWithOptions()
+}
+
+// NewDeepSeekClientWithOptions creates DeepSeek client (supports options pattern)
+func NewDeepSeekClientWithOptions(opts ...mcp.ClientOption) mcp.AIClient {
+	deepseekOpts := []mcp.ClientOption{
+		mcp.WithProvider(mcp.ProviderDeepSeek),
+		mcp.WithModel(mcp.DefaultDeepSeekModel),
+		mcp.WithBaseURL(mcp.DefaultDeepSeekBaseURL),
+	}
+
+	allOpts := append(deepseekOpts, opts...)
+	baseClient := mcp.NewClient(allOpts...).(*mcp.Client)
+
+	dsClient := &DeepSeekClient{
+		Client: baseClient,
+	}
+
+	baseClient.Hooks = dsClient
+	return dsClient
+}
+
+func (dsClient *DeepSeekClient) SetAPIKey(apiKey string, customURL string, customModel string) {
+	dsClient.APIKey = apiKey
+
+	if len(apiKey) > 8 {
+		dsClient.Log.Infof("🔧 [MCP] DeepSeek API Key: %s...%s", apiKey[:4], apiKey[len(apiKey)-4:])
+	}
+	if customURL != "" {
+		dsClient.BaseURL = customURL
+		dsClient.Log.Infof("🔧 [MCP] DeepSeek using custom BaseURL: %s", customURL)
+	} else {
+		dsClient.Log.Infof("🔧 [MCP] DeepSeek using default BaseURL: %s", dsClient.BaseURL)
+	}
+	if customModel != "" {
+		dsClient.Model = customModel
+		dsClient.Log.Infof("🔧 [MCP] DeepSeek using custom Model: %s", customModel)
+	} else {
+		dsClient.Log.Infof("🔧 [MCP] DeepSeek using default Model: %s", dsClient.Model)
+	}
+}
+
+func (dsClient *DeepSeekClient) SetAuthHeader(reqHeaders http.Header) {
+	dsClient.Client.SetAuthHeader(reqHeaders)
+}