feat: 交付官方 Docker 运行时，外观改背景图并下线自定义 CSS/JS

站点/后台分轨背景与用户列表排序一并落地；生产 CORS 改走 SITE_URL，健康检查带版本号。

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

frontend/lib/theme.ts

@@ -157,7 +157,7 @@ function clampForLight(hex: string): string {
 function deriveDark(hex: string): string {
   const [h, s, lRaw] = rgbToHsl(hexToRgb(hex));
   let l = Math.max(lRaw, 0.62);
-  const surfaces = ["#181b21", "#101211", "#10162b"];
+  const surfaces = ["#181b21", "#0c0d10", "#10162b"];
   let cur = hex;
   for (let i = 0; i < 120; i++) {
     cur = rgbToHex(hslToRgb([h, s, l]));
@@ -207,7 +207,7 @@ function buildAccentCSS(input: string): string {
     `--accent-hi:${hi};`,
     `--accent-soft:${rgba(light, 0.1)};`,
     `--accent-on:#ffffff;`,
-    `--nav-active-bg:var(--panel);`,
+    `--nav-active-bg:${rgba(light, 0.1)};`,
     `--nav-active-ink:${light};`,
     `--nav-active-line:${rgba(light, 0.38)};`,
     `}`,
@@ -216,7 +216,7 @@ function buildAccentCSS(input: string): string {
     `--accent-hi:${darkHi};`,
     `--accent-soft:${rgba(dark, 0.16)};`,
     `--accent-on:#10162b;`,
-    `--nav-active-bg:var(--panel);`,
+    `--nav-active-bg:${rgba(dark, 0.14)};`,
     `--nav-active-ink:${darkHi};`,
     `--nav-active-line:${rgba(dark, 0.38)};`,
     `}`,