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/components/auth/RegistrationDisabled.test.tsx

@@ -0,0 +1,103 @@
+import { describe, it, expect, vi } from 'vitest'
+import { render, screen, fireEvent } from '@testing-library/react'
+import { RegistrationDisabled } from './RegistrationDisabled'
+import { LanguageProvider } from '../../contexts/LanguageContext'
+
+// Mock useLanguage hook
+vi.mock('../../contexts/LanguageContext', async () => {
+  const actual = await vi.importActual('../../contexts/LanguageContext')
+  return {
+    ...actual,
+    useLanguage: () => ({ language: 'en' }),
+  }
+})
+
+/**
+ * RegistrationDisabled Component Tests
+ *
+ * Tests the component that displays when registration is disabled
+ * This is part of the registration toggle feature
+ */
+describe('RegistrationDisabled Component', () => {
+  const renderComponent = () => {
+    return render(
+      <LanguageProvider>
+        <RegistrationDisabled />
+      </LanguageProvider>
+    )
+  }
+
+  describe('Rendering', () => {
+    it('should render the component without errors', () => {
+      const { container } = renderComponent()
+      expect(container).toBeTruthy()
+    })
+
+    it('should display the NoFx logo', () => {
+      renderComponent()
+      const logo = screen.getByAltText('NoFx Logo')
+      expect(logo).toBeTruthy()
+      expect(logo.getAttribute('src')).toBe('/icons/nofx.svg')
+    })
+
+    it('should display registration closed heading', () => {
+      renderComponent()
+      const heading = screen.getByText('Registration Closed')
+      expect(heading).toBeTruthy()
+    })
+
+    it('should display registration closed message', () => {
+      renderComponent()
+      const message = screen.getByText(/User registration is currently disabled/i)
+      expect(message).toBeTruthy()
+    })
+
+    it('should display back to login button', () => {
+      renderComponent()
+      const button = screen.getByRole('button', { name: /back to login/i })
+      expect(button).toBeTruthy()
+    })
+  })
+
+  describe('Navigation', () => {
+    it('should navigate to login page when button is clicked', () => {
+      const pushStateSpy = vi.spyOn(window.history, 'pushState')
+      const dispatchEventSpy = vi.spyOn(window, 'dispatchEvent')
+
+      renderComponent()
+      const button = screen.getByRole('button', { name: /back to login/i })
+
+      fireEvent.click(button)
+
+      expect(pushStateSpy).toHaveBeenCalledWith({}, '', '/login')
+      expect(dispatchEventSpy).toHaveBeenCalled()
+
+      pushStateSpy.mockRestore()
+      dispatchEventSpy.mockRestore()
+    })
+  })
+
+  describe('Styling', () => {
+    it('should have correct background color', () => {
+      const { container } = renderComponent()
+      const mainDiv = container.firstChild as HTMLElement
+      // Browser converts hex to rgb
+      expect(mainDiv.style.background).toMatch(/rgb\(11,\s*14,\s*17\)|#0B0E11/i)
+    })
+
+    it('should have correct text color', () => {
+      const { container } = renderComponent()
+      const mainDiv = container.firstChild as HTMLElement
+      // Browser converts hex to rgb
+      expect(mainDiv.style.color).toMatch(/rgb\(234,\s*236,\s*239\)|#EAECEF/i)
+    })
+
+    it('should have centered layout', () => {
+      const { container } = renderComponent()
+      const mainDiv = container.firstChild as HTMLElement
+      expect(mainDiv.className).toContain('flex')
+      expect(mainDiv.className).toContain('items-center')
+      expect(mainDiv.className).toContain('justify-center')
+    })
+  })
+})