feat: 完成头像上传、站点主题配置与UI优化

- 新增附件模型与上传服务，拆分头像上传/管理逻辑
- 重构用户资料接口，移除直接修改头像字段，改用专用上传接口
- 添加站点公开设置API与管理员外观配置页
- 全局替换hover背景为accent-soft，优化交互一致性
- 完善头像组件，支持图片加载失败回退与src更新重置
- 新增用户状态事件总线，解决同页头像更新不及时问题
- 调整依赖包顺序与CI依赖版本
- 重构板块列表接口，新增帖子计数
- 迁移账号设置到用户主页tab，合并重复代码

frontend/components/home/WorkspaceNav.tsx

@@ -2,7 +2,7 @@
 
 import Link from "next/link";
 import { useSearchParams } from "next/navigation";
-import { PenSquare, Home } from "lucide-react";
+import { PenSquare, Home, ChevronRight } from "lucide-react";
 import type { BoardWithCount, User } from "@/lib/api";
 
 // 首页壳内板块切换：仅替换中栏帖子流，不离开工作台
@@ -23,64 +23,62 @@ export function WorkspaceNav({ boards, user }: { boards: BoardWithCount[]; user:
           <PenSquare size={16} /> 发起讨论
         </Link>
 
-        {/* 「全部讨论」是重置筛选的动作入口，与板块目录分区展示 */}
+        {/* 「全部讨论」是重置筛选的动作入口，与板块目录分区展示；卡片样式与下方板块一致 */}
         <div className="space-y-0.5">
-          <Link
-            href="/"
-            className="j13-raillink"
-            aria-current={activeBoard === 0 ? "page" : undefined}
-          >
-            <Home size={16} className="shrink-0" />
-            <span className="flex-1 truncate">全部讨论</span>
+          <Link href="/" className="j13-bcard" aria-current={activeBoard === 0 ? "page" : undefined}>
+            <span
+              className="j13-bcard-ico"
+              style={{ background: "var(--accent-soft)", color: "var(--accent)" }}
+              aria-hidden="true"
+            >
+              <Home size={16} />
+            </span>
+            <span className="j13-bcard-name flex-1 truncate text-[13px] font-bold">
+              全部讨论
+            </span>
           </Link>
         </div>
 
-        {/* 板块目录：发现型入口（介绍 + 讨论量），区别于帖子页面包屑的位置指引；
-            点击不离开工作台，仅在中栏筛选该板块帖子流 */}
+        {/* 板块目录：标题可点击进入板块汇总列表页（/boards）；
+            下方板块卡片点击不离开工作台，仅在中栏筛选该板块帖子流 */}
         <div>
-          <p
-            className="px-1 mb-2 flex items-center justify-between text-[11.5px] font-bold tracking-[0.08em] uppercase"
-            style={{ color: "var(--ink-3)" }}
+          <Link
+            href="/boards"
+            className="group px-1 mb-2 flex items-center justify-between text-[11.5px] font-bold tracking-[0.08em] uppercase text-[var(--ink-3)] hover:text-[var(--accent)] transition-colors"
+            aria-label="进入板块目录列表页"
           >
-            <span>板块目录</span>
+            <span className="flex items-center">
+              <span>板块目录</span>
+              <ChevronRight
+                size={12}
+                className="ml-0.5 opacity-0 -translate-x-0.5 group-hover:opacity-100 group-hover:translate-x-0 transition-all"
+                aria-hidden="true"
+              />
+            </span>
             {boards.length > 0 && (
               <span className="tracking-normal font-semibold tabular-nums">{boards.length} 个</span>
             )}
-          </p>
+          </Link>
           <div className="space-y-2">
-            {boards.map((b, i) => {
-              const desc = b.description?.trim();
-              return (
-                <Link
-                  key={b.id}
-                  href={boardHref(b.id)}
-                  className="j13-bcard"
-                  aria-current={activeBoard === b.id ? "page" : undefined}
-                  aria-label={`${b.name}板块，${b.post_count} 篇讨论`}
-                >
-                  <span
-                    className={`av-${i % 8} j13-bcard-ico`}
-                    aria-hidden="true"
-                  >
-                    {b.name.slice(0, 1)}
+            {boards.map((b, i) => (
+              <Link
+                key={b.id}
+                href={boardHref(b.id)}
+                className="j13-bcard"
+                aria-current={activeBoard === b.id ? "page" : undefined}
+                aria-label={`${b.name}板块，${b.post_count} 篇讨论`}
+              >
+                <span className={`av-${i % 8} j13-bcard-ico`} aria-hidden="true">
+                  {b.name.slice(0, 1)}
+                </span>
+                <span className="min-w-0 flex-1 flex items-center justify-between gap-2">
+                  <span className="j13-bcard-name truncate text-[13px] font-bold">
+                    {b.name}
                   </span>
-                  <span className="min-w-0 flex-1">
-                    <span className="flex items-center justify-between gap-2">
-                      <span
-                        className="truncate text-[13px] font-bold"
-                        style={{ color: "var(--ink)" }}
-                      >
-                        {b.name}
-                      </span>
-                      <span className="meta shrink-0 text-[11px] tabular-nums">
-                        {b.post_count} 篇
-                      </span>
-                    </span>
-                    {desc && <span className="j13-bcard-desc">{desc}</span>}
-                  </span>
-                </Link>
-              );
-            })}
+                  <span className="meta shrink-0 text-[11px] tabular-nums">{b.post_count} 篇</span>
+                </span>
+              </Link>
+            ))}
           </div>
         </div>
       </div>