feat(core/frontend): pipeline stage editor (burn-in controls) + double-submit guard & button greying

Pipeline (脚本→资产→故事板→视频→拼接):
- Stage1 render real script shots + wire 确认脚本→adopt (advance stage)
- Stage2 add person/scene AI-生成 buttons + clickable category tabs
- Stage4 auto-poll videos to completion + per-segment upload + real frame thumbnails + download
- Stage5 real timeline editor: clips undo/redo/split/copy/delete/drag-reorder/zoom,
  subtitle style + per-clip text editor, transition select (xfade preview),
  BGM upload + volume, save draft, export-with-save → shows/download final MP4
- embedded asset URLs everywhere (beat assets pagination)

UX: re-entry guard in action() (no double-submit anywhere) + greyed :disabled
styles for btn-aigen/chat-mode/pill-cta/tl-action so generate buttons visibly
disable while generating.

Also includes prior uncommitted frontend work: settings preferences/sessions/avatar,
asset delete, account/team/products pages, fonts.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

core/frontend/public/exact/assets/restraint.css

@@ -13,7 +13,8 @@
   src: local('Alibaba PuHuiTi 3.0'),
        local('AlibabaPuHuiTi-3-55-Regular'),
        local('Alibaba PuHuiTi 2.0'),
-       local('AlibabaPuHuiTi-2-55-Regular');
+       local('AlibabaPuHuiTi-2-55-Regular'),
+       url('/fonts/AlibabaPuHuiTi-3-55-Regular.woff2') format('woff2');
 }
 @font-face {
   font-family: 'Alibaba PuHuiTi';
@@ -22,7 +23,8 @@
   font-display: swap;
   src: local('Alibaba PuHuiTi 3.0 Medium'),
        local('AlibabaPuHuiTi-3-65-Medium'),
-       local('AlibabaPuHuiTi-2-65-Medium');
+       local('AlibabaPuHuiTi-2-65-Medium'),
+       url('/fonts/AlibabaPuHuiTi-3-65-Medium.woff2') format('woff2');
 }
 @font-face {
   font-family: 'Alibaba PuHuiTi';
@@ -30,7 +32,8 @@
   font-style: normal;
   font-display: swap;
   src: local('AlibabaPuHuiTi-3-75-SemiBold'),
-       local('AlibabaPuHuiTi-2-75-SemiBold');
+       local('AlibabaPuHuiTi-2-75-SemiBold'),
+       url('/fonts/AlibabaPuHuiTi-3-75-SemiBold.woff2') format('woff2');
 }
 @font-face {
   font-family: 'Alibaba PuHuiTi';
@@ -39,7 +42,8 @@
   font-display: swap;
   src: local('Alibaba PuHuiTi 3.0 Bold'),
        local('AlibabaPuHuiTi-3-85-Bold'),
-       local('AlibabaPuHuiTi-2-85-Bold');
+       local('AlibabaPuHuiTi-2-85-Bold'),
+       url('/fonts/AlibabaPuHuiTi-3-85-Bold.woff2') format('woff2');
 }
 
 * { box-sizing: border-box; margin: 0; padding: 0; }