fix(frontend): Phase 9 — restore index dashboard, fix login/CSRF, port legacy styles

- Index dashboard regains the 8 cards that were lost in the SPA port
  (3X-UI panel info, Operation Hours, System Load, Usage, Overall Speed,
  Total Data, IP Addresses, Connection Stats), plus a Config button that
  shows the live xray config.json. Version display falls back through
  panelUpdateInfo → window.__X_UI_CUR_VER__ → '?' so dev mode isn't blank.
- Xray config no longer hangs on load: useXraySetting surfaces failures
  instead of leaving a perpetual spinner, and the Vite dev proxy stops
  hijacking POST requests to migrated routes (only GETs get bypassed).
- Inbound page no longer throws __asyncLoader/emitsOptions errors —
  inbound.js was missing imports (NumberFormatter, SizeFormatter,
  Wireguard) and InboundList kept emitting after unmount.
- Login round-trip works after logout: a public /csrf-token endpoint
  bootstraps the SPA before authentication, axios caches the token
  module-level, and the dev 401 handler navigates to /login.html
  instead of reloading the dashboard into a redirect loop.
- legacy.css mirrors the legacy panel's surface/text variables so dark
  and ultra-dark themes match main; every SPA entry imports it.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

web/controller/index.go

@@ -40,6 +40,12 @@ func NewIndexController(g *gin.RouterGroup) *IndexController {
 func (a *IndexController) initRouter(g *gin.RouterGroup) {
 	g.GET("/", a.index)
 	g.GET("/logout", a.logout)
+	// Public CSRF endpoint — the SPA login page (served by Vite in
+	// dev or by serveDistPage in prod) needs a token to POST /login,
+	// but the panel-side /panel/csrf-token sits behind checkLogin.
+	// EnsureCSRFToken creates a session token even for anonymous
+	// callers, so any pre-login flow can bootstrap from here.
+	g.GET("/csrf-token", a.csrfToken)
 
 	g.POST("/login", middleware.CSRFMiddleware(), a.login)
 	g.POST("/getTwoFactorEnable", middleware.CSRFMiddleware(), a.getTwoFactorEnable)
@@ -148,6 +154,17 @@ func (a *IndexController) logout(c *gin.Context) {
 	c.Redirect(http.StatusTemporaryRedirect, c.GetString("base_path"))
 }
 
+// csrfToken returns the session CSRF token. Public — the login page
+// needs a token before authenticating.
+func (a *IndexController) csrfToken(c *gin.Context) {
+	token, err := session.EnsureCSRFToken(c)
+	if err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"success": false, "msg": err.Error()})
+		return
+	}
+	c.JSON(http.StatusOK, gin.H{"success": true, "obj": token})
+}
+
 // getTwoFactorEnable retrieves the current status of two-factor authentication.
 func (a *IndexController) getTwoFactorEnable(c *gin.Context) {
 	status, err := a.settingService.GetTwoFactorEnable()