Speed up top nav with turbo routing and external base CSS.

Remove view-transition lag, swap main content without full reload, prefetch pages, and tear down SSE timers on leave.

Co-authored-by: Cursor <cursoragent@cursor.com>

static/css/tech.css

@@ -1,25 +1,8 @@
 /* Copyright (c) 2025-2026 马建军. All rights reserved. 专有软件，详见 LICENSE.zh-CN.txt */
 /* 科技感增强层 — 与 base.html 变量配合 */
 
-@view-transition {
-    navigation: auto;
-}
-
-::view-transition-old(app-main),
-::view-transition-new(app-main) {
-    animation-duration: .18s;
-}
-
-::view-transition-old(app-tech-bg),
-::view-transition-new(app-tech-bg),
-::view-transition-old(site-header),
-::view-transition-new(site-header) {
-    animation: none;
-}
-
 .tech-bg{
     position:fixed;inset:0;z-index:0;pointer-events:none;overflow:hidden;
-    view-transition-name:app-tech-bg;
 }
 .tech-grid{
     position:absolute;inset:0;
@@ -70,13 +53,14 @@
     .tech-glow,.tech-glow-2,.tech-scanline,.card::after,.site-header::after{animation:none}
 }
 
+.main.nav-loading{opacity:.75;pointer-events:none;transition:opacity .12s}
+
 .page-wrap{position:relative;z-index:1}
 
 .site-header{
     border-bottom:1px solid var(--border-header);
     background:transparent;
     backdrop-filter:none;
-    view-transition-name:site-header;
 }
 .site-header::after{
     content:"";display:block;height:1px;margin-top:-1px;