feat: move SaaS app to /platform base path, Logto becomes catch-all

Eliminates all Logto path enumeration in Traefik. Routing is now:
- /platform/* → cameleer-saas (SPA + API)
- /server/* → server-ui
- /* (catch-all) → Logto (sign-in, OIDC, assets, everything)

Spring context-path handles backend prefix transparently. No changes
needed in controllers, SecurityConfig, or interceptors.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/main.tsx

@@ -80,7 +80,7 @@ function App() {
     >
       <TokenSync resource={config.logtoResource} />
       <QueryClientProvider client={queryClient}>
-        <BrowserRouter>
+        <BrowserRouter basename="/platform">
           <AppRouter />
         </BrowserRouter>
       </QueryClientProvider>