feat: 帖子收藏与用户关注

- 新增收藏功能：favorite 服务与 handler、FavoriteButton 组件
- 新增关注功能：follow 服务与 handler、FollowButton 组件
- 用户主页适配关注/粉丝与收藏展示
- flash 消息工具、广告与侧边栏组件微调

frontend/components/home/CommunityPanels.tsx

@@ -34,7 +34,13 @@ import { FRIEND_LINKS } from "@/lib/friendLinks";
 import { formatCompact, formatShortDate } from "@/lib/format";
 import { pageGlyph } from "@/lib/pageGlyph";
 import { AboutSiteHeader } from "@/components/site-doc";
-import { AD_IMAGE_HEIGHT, AD_IMAGE_SIZE_LABEL, AD_IMAGE_WIDTH } from "@/lib/ads";
+import {
+  AD_IMAGE_HEIGHT,
+  AD_IMAGE_SIZE_LABEL,
+  AD_IMAGE_WIDTH,
+  AD_TIP_DELAY_MS,
+  adHoverTip,
+} from "@/lib/ads";
 
 /* ---------- 站点数据（2×2 bento 统计瓦片） ---------- */
 
@@ -464,10 +470,7 @@ export function AdsPanel({
       <p className="j13-module-title mb-3">
         <CircleDollarSign size={15} style={{ color: "var(--accent)" }} />
         {title || "自助推广"}
-        <Link
-          href="/ads/buy"
-          className="meta ml-auto text-[12px] font-normal transition-colors hover:text-[var(--accent)]"
-        >
+        <Link href="/ads/buy" className="j13-ad-buy-btn ml-auto">
           购买广告位
         </Link>
       </p>
@@ -482,6 +485,8 @@ export function AdsPanel({
                   target="_blank"
                   rel="noopener noreferrer sponsored"
                   className="j13-ad-image-link"
+                  data-tip={adHoverTip(ad.ends_at)}
+                  data-tip-delay={AD_TIP_DELAY_MS}
                 >
                   {/* eslint-disable-next-line @next/next/no-img-element */}
                   <img
@@ -513,6 +518,7 @@ export function AdsPanel({
                   textColor={ad.text_color || "#1E293B"}
                   bgColor={ad.bg_color || "#F1F5F9"}
                   href={ad.link_url}
+                  endsAt={ad.ends_at}
                 />
               </li>
             ) : (