feat(platform): Implement legacy system integration with Wrapper Bridge architecture

Complete integration of the old clinical research platform (www.xunzhengyixue.com)
into the new AI platform via Token injection + iframe embedding:

Backend:
- Add legacy-bridge module (MySQL pool, auth service, routes)
- POST /api/v1/legacy/auth: JWT -> phone lookup -> Token injection into old MySQL
- Auto-create user in old system if not found (matched by phone number)

Frontend:
- LegacySystemPage: iframe container with Bridge URL construction
- ResearchManagement + StatisticalTools entry components
- Module registry updated from external links to iframe embed mode

ECS (token-bridge.html deployed to www.xunzhengyixue.com):
- Wrapper Bridge: sets cookies within same-origin context
- Storage Access API for cross-site dev environments
- CSS injection: hide old system nav/footer, remove padding gaps
- Inner iframe loads target page with full DOM access (same-origin)

Key technical decisions:
- Token injection (direct MySQL write) instead of calling login API
- Wrapper Bridge instead of parent-page cookie setting (cross-origin fix)
- Storage Access API + SameSite=None;Secure for third-party cookie handling
- User isolation guaranteed by phone number matching

Documentation:
- Integration plan v4.0 with full implementation record
- Implementation summary with 6 pitfalls documented
- System status guide updated (ST module now integrated)

Tested: Local E2E verified - auto login, research management, 126 statistical
tools, report generation, download, UI layout all working correctly

Made-with: Cursor

frontend-v2/src/App.tsx

@@ -83,17 +83,21 @@ function App() {
                   <Route index element={<HomePage />} />
                   
                   {/* 动态加载模块路由 - 基于模块权限系统 ⭐ 2026-01-16 */}
-                  {MODULES.map(module => (
+                  {MODULES.filter(m => !m.isExternal).map(module => (
                     <Route
                       key={module.id}
                       path={`${module.path}/*`}
                       element={
-                        <RouteGuard
-                          requiredModule={module.moduleCode}
-                          moduleName={module.name}
-                        >
+                        module.isLegacyEmbed ? (
                           <module.component />
-                        </RouteGuard>
+                        ) : (
+                          <RouteGuard
+                            requiredModule={module.moduleCode}
+                            moduleName={module.name}
+                          >
+                            <module.component />
+                          </RouteGuard>
+                        )
                       }
                     />
                   ))}