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/app/boards/page.tsx

@@ -0,0 +1,108 @@
+import Link from "next/link";
+import type { Metadata } from "next";
+import { ChevronRight, MessagesSquare, LayoutGrid } from "lucide-react";
+import { fetchBoards } from "@/lib/api";
+
+export const metadata: Metadata = {
+  title: "板块目录 · 姜十三论坛",
+  description: "浏览论坛全部板块，找到感兴趣的话题社区",
+};
+
+// 板块汇总列表页：首页左栏「板块目录」标题的落地页，
+// 展示全部板块（介绍 + 讨论量），点击进入板块独立页
+export default async function BoardsPage() {
+  const { boards } = await fetchBoards();
+  const totalPosts = boards.reduce((sum, b) => sum + (b.post_count || 0), 0);
+
+  return (
+    <div>
+      {/* 面包屑 */}
+      <nav className="meta mb-5 flex items-center gap-1.5 text-[13px]">
+        <Link href="/" className="hover:text-[var(--accent)] transition-colors">首页</Link>
+        <ChevronRight size={13} />
+        <span style={{ color: "var(--accent)" }}>板块目录</span>
+      </nav>
+
+      {/* 页头 */}
+      <div className="panel p-6 sm:p-7 mb-6 relative overflow-hidden">
+        <span
+          aria-hidden
+          className="absolute -top-16 -right-12 w-48 h-48 rounded-full"
+          style={{ background: "var(--accent-soft)" }}
+        />
+        <div className="relative flex items-center gap-4">
+          <span
+            className="w-14 h-14 sm:w-16 sm:h-16 rounded-2xl flex items-center justify-center shrink-0"
+            style={{ background: "var(--accent-soft)", color: "var(--accent)" }}
+          >
+            <LayoutGrid size={28} />
+          </span>
+          <div>
+            <h1 className="text-2xl sm:text-[28px] font-extrabold tracking-tight" style={{ color: "var(--ink)" }}>
+              板块目录
+            </h1>
+            <p className="meta mt-1.5">
+              共 {boards.length} 个板块 · {totalPosts} 篇讨论
+            </p>
+          </div>
+        </div>
+      </div>
+
+      {/* 板块卡片网格 */}
+      {boards.length === 0 ? (
+        <div className="panel text-center py-20 px-6">
+          <span
+            className="inline-flex w-14 h-14 rounded-full items-center justify-center mb-4"
+            style={{ background: "var(--accent-soft)", color: "var(--accent)" }}
+          >
+            <MessagesSquare size={26} />
+          </span>
+          <p className="font-bold text-lg" style={{ color: "var(--ink)" }}>还没有任何板块</p>
+          <p className="meta mt-1.5">板块由管理员创建，敬请期待</p>
+        </div>
+      ) : (
+        <div className="grid grid-cols-1 sm:grid-cols-2 lg:grid-cols-3 gap-4">
+          {boards.map((b, i) => (
+            <Link
+              key={b.id}
+              href={`/board/${b.id}`}
+              className="j13-module group flex items-start gap-3.5 transition-[border-color,background] duration-150 hover:border-[var(--nav-active-line)] hover:bg-[var(--accent-soft)] focus-visible:bg-[var(--accent-soft)]"
+              aria-label={`${b.name}板块，${b.post_count} 篇讨论`}
+            >
+              <span className={`av-${i % 8} j13-bcard-ico !w-11 !h-11 !text-lg`} aria-hidden="true">
+                {b.name.slice(0, 1)}
+              </span>
+              <span className="min-w-0 flex-1">
+                <span className="flex items-center justify-between gap-2">
+                  <span className="truncate text-[15px] font-extrabold" style={{ color: "var(--ink)" }}>
+                    {b.name}
+                  </span>
+                  <span className="meta shrink-0 text-[11.5px] tabular-nums">{b.post_count} 篇</span>
+                </span>
+                {b.description?.trim() && (
+                  <span
+                    className="block mt-1 text-[12.5px] leading-relaxed line-clamp-2"
+                    style={{ color: "var(--ink-3)" }}
+                  >
+                    {b.description.trim()}
+                  </span>
+                )}
+                <span
+                  className="mt-2.5 inline-flex items-center gap-0.5 text-[12px] font-bold transition-colors group-hover:text-[var(--accent)]"
+                  style={{ color: "var(--ink-2)" }}
+                >
+                  进入板块
+                  <ChevronRight
+                    size={12}
+                    className="transition-transform group-hover:translate-x-0.5"
+                    aria-hidden="true"
+                  />
+                </span>
+              </span>
+            </Link>
+          ))}
+        </div>
+      )}
+    </div>
+  );
+}