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/minimax.go

@@ -0,0 +1,73 @@
+package provider
+
+import (
+	"net/http"
+
+	"nofx/mcp"
+)
+
+const (
+	DefaultMiniMaxBaseURL = "https://api.minimax.io/v1"
+	DefaultMiniMaxModel   = "MiniMax-M2.5"
+)
+
+func init() {
+	mcp.RegisterProvider(mcp.ProviderMiniMax, func(opts ...mcp.ClientOption) mcp.AIClient {
+		return NewMiniMaxClientWithOptions(opts...)
+	})
+}
+
+type MiniMaxClient struct {
+	*mcp.Client
+}
+
+func (c *MiniMaxClient) BaseClient() *mcp.Client { return c.Client }
+
+// NewMiniMaxClient creates MiniMax client (backward compatible)
+func NewMiniMaxClient() mcp.AIClient {
+	return NewMiniMaxClientWithOptions()
+}
+
+// NewMiniMaxClientWithOptions creates MiniMax client (supports options pattern)
+func NewMiniMaxClientWithOptions(opts ...mcp.ClientOption) mcp.AIClient {
+	minimaxOpts := []mcp.ClientOption{
+		mcp.WithProvider(mcp.ProviderMiniMax),
+		mcp.WithModel(DefaultMiniMaxModel),
+		mcp.WithBaseURL(DefaultMiniMaxBaseURL),
+	}
+
+	allOpts := append(minimaxOpts, opts...)
+	baseClient := mcp.NewClient(allOpts...).(*mcp.Client)
+
+	minimaxClient := &MiniMaxClient{
+		Client: baseClient,
+	}
+
+	baseClient.Hooks = minimaxClient
+	return minimaxClient
+}
+
+func (c *MiniMaxClient) SetAPIKey(apiKey string, customURL string, customModel string) {
+	c.APIKey = apiKey
+
+	if len(apiKey) > 8 {
+		c.Log.Infof("🔧 [MCP] MiniMax API Key: %s...%s", apiKey[:4], apiKey[len(apiKey)-4:])
+	}
+	if customURL != "" {
+		c.BaseURL = customURL
+		c.Log.Infof("🔧 [MCP] MiniMax using custom BaseURL: %s", customURL)
+	} else {
+		c.Log.Infof("🔧 [MCP] MiniMax using default BaseURL: %s", c.BaseURL)
+	}
+	if customModel != "" {
+		c.Model = customModel
+		c.Log.Infof("🔧 [MCP] MiniMax using custom Model: %s", customModel)
+	} else {
+		c.Log.Infof("🔧 [MCP] MiniMax using default Model: %s", c.Model)
+	}
+}
+
+// MiniMax uses standard OpenAI-compatible API with Bearer auth
+func (c *MiniMaxClient) SetAuthHeader(reqHeaders http.Header) {
+	c.Client.SetAuthHeader(reqHeaders)
+}