feat: 首页 Go SSR 与 React hydrate 同构，消壳层与帖行闪动

补齐侧栏/右栏图标与徽章、鉴权种子、StaticFeedList，并修正嵌套 a 与标题徽章对齐。

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

frontend/src/main.tsx

@@ -1,22 +1,89 @@
 import React from 'react';
-import ReactDOM from 'react-dom/client';
+import { hydrateRoot, createRoot } from 'react-dom/client';
 import { applyTheme, getStoredTheme } from './utils/theme';
 import App from './App';
+import { consumeHomeBoot } from './utils/homeBoot';
+import { beginHomeHydrate } from './utils/homeHydrate';
 import { ensureColdBootReady, isMainLayoutPath } from './utils/prefetchRoute';
 
 applyTheme(getStoredTheme());
+consumeHomeBoot();
 
-async function boot() {
-  const path = `${window.location.pathname}${window.location.search}`;
-  // 前台：齐套前不挂载；完成后一次 createRoot
-  if (isMainLayoutPath(window.location.pathname)) {
-    await ensureColdBootReady(path);
-  }
-  ReactDOM.createRoot(document.getElementById('root')!).render(
+function hasSSRHome(): boolean {
+  return !!document.querySelector('#root .ssr-home');
+}
+
+function waitForStylesheets(): Promise<void> {
+  const links = Array.from(document.querySelectorAll('link[rel="stylesheet"]'));
+  if (links.length === 0) return Promise.resolve();
+  return Promise.all(
+    links.map(
+      (node) =>
+        new Promise<void>((resolve) => {
+          const link = node as HTMLLinkElement;
+          try {
+            if (link.sheet) {
+              resolve();
+              return;
+            }
+          } catch {
+            /* cross-origin */
+          }
+          const finish = () => resolve();
+          link.addEventListener('load', finish, { once: true });
+          link.addEventListener('error', finish, { once: true });
+        }),
+    ),
+  ).then(() => undefined);
+}
+
+function renderApp() {
+  return (
     <React.StrictMode>
       <App />
-    </React.StrictMode>,
+    </React.StrictMode>
   );
 }
 
+function mountCreateRoot(el: HTMLElement) {
+  createRoot(el).render(renderApp());
+}
+
+/** 有 SSR 正文：hydrate 接管同一 DOM；失败则回退 createRoot */
+function mountHydrateHome(el: HTMLElement) {
+  beginHomeHydrate();
+  try {
+    hydrateRoot(el, renderApp());
+  } catch (err) {
+    console.warn('[j13] hydrateRoot 失败，回退 createRoot', err);
+    el.innerHTML = '';
+    mountCreateRoot(el);
+  }
+}
+
+async function boot() {
+  const path = `${window.location.pathname}${window.location.search}`;
+  const ssr = hasSSRHome();
+
+  await waitForStylesheets();
+  try {
+    if (document.fonts?.ready) await document.fonts.ready;
+  } catch {
+    /* ignore */
+  }
+
+  if (isMainLayoutPath(window.location.pathname)) {
+    await ensureColdBootReady(path);
+  }
+
+  const root = document.getElementById('root');
+  if (!root) return;
+
+  if (ssr) {
+    mountHydrateHome(root);
+  } else {
+    mountCreateRoot(root);
+  }
+}
+
 void boot();