feat: 用户徽章与等级体系，积分经济管理重构

- 新增徽章系统：badge 服务与 handler、管理端配置页、BadgeChip/LevelBadge 展示组件
- 新增等级模型：model/level 及前端 levels 元数据
- 管理端经济模块拆分为 points/badges/levels 独立页面，EconomySettings 迁入设置
- 积分、签到、评论等服务适配等级与徽章逻辑

frontend/app/admin/levels/LevelsAdmin.tsx

@@ -0,0 +1,309 @@
+"use client";
+
+import { useEffect, useMemo, useState } from "react";
+import { Plus, RotateCcw, Trash2 } from "lucide-react";
+import { AdminStepper, AdminSwitch } from "@/components/admin";
+import ConfirmDialog from "@/components/ConfirmDialog";
+import useUnsavedGuard from "@/hooks/useUnsavedGuard";
+import { apiGetSettings, apiUpdateSiteSettings } from "@/lib/api";
+import {
+  DEFAULT_LEVEL_DEFS,
+  LEVEL_BADGE_CLASS,
+  LEVEL_COLOR_KEYS,
+  LEVEL_COLOR_TOKENS,
+  MAX_LEVEL_COUNT,
+  splitBackground,
+  type LevelDef,
+} from "@/lib/levels";
+import { toast } from "@/lib/toast";
+
+const cloneDefs = (defs: LevelDef[]): LevelDef[] =>
+  defs.map((d) => ({ threshold: d.threshold, color: d.color }));
+
+const sameDefs = (a: LevelDef[] | null, b: LevelDef[] | null) => {
+  if (a === b) return true;
+  if (!a || !b || a.length !== b.length) return false;
+  return a.every((d, i) => d.threshold === b[i].threshold && d.color === b[i].color);
+};
+
+/** 等级管理：配置等级数量（2–12）、每级所需累计积分与前景/背景配色、特效开关 */
+export default function LevelsAdmin() {
+  const [form, setForm] = useState<LevelDef[] | null>(null); // null = 加载中
+  const [saved, setSaved] = useState<LevelDef[] | null>(null);
+  const [fx, setFx] = useState(true);
+  const [savedFx, setSavedFx] = useState(true);
+  const [resetOpen, setResetOpen] = useState(false);
+  const [saving, setSaving] = useState(false);
+  const dirty = useMemo(
+    () => !sameDefs(form, saved) || fx !== savedFx,
+    [form, saved, fx, savedFx],
+  );
+  const leave = useUnsavedGuard(dirty);
+
+  useEffect(() => {
+    let alive = true;
+    apiGetSettings()
+      .then((s) => {
+        if (!alive) return;
+        const defs = cloneDefs(s.levels);
+        setForm(defs);
+        setSaved(defs);
+        setFx(s.levels_fx);
+        setSavedFx(s.levels_fx);
+      })
+      .catch((e) => {
+        toast(e instanceof Error ? e.message : "获取等级配置失败");
+        if (alive) setForm([]);
+      });
+    return () => {
+      alive = false;
+    };
+  }, []);
+
+  const setThreshold = (i: number, v: number) =>
+    setForm((f) => (f ? f.map((d, j) => (j === i ? { ...d, threshold: v } : d)) : f));
+  const setColor = (i: number, color: string) =>
+    setForm((f) => (f ? f.map((d, j) => (j === i ? { ...d, color } : d)) : f));
+  const addLevel = () =>
+    setForm((f) => {
+      if (!f || f.length >= MAX_LEVEL_COUNT) return f;
+      const last = f[f.length - 1];
+      return [...f, { threshold: (last?.threshold ?? 0) + 100, color: "neutral" }];
+    });
+  const removeLast = () =>
+    setForm((f) => (f && f.length > 2 ? f.slice(0, -1) : f));
+
+  const save = async () => {
+    if (saving || !dirty || !form) return;
+    if (form.length < 2) {
+      toast("至少保留 2 个等级");
+      return;
+    }
+    if (form[0].threshold !== 0) {
+      toast("Lv.1 所需积分须为 0");
+      return;
+    }
+    for (let i = 1; i < form.length; i++) {
+      if (!(form[i].threshold > form[i - 1].threshold)) {
+        toast(`Lv.${i + 1} 所需积分须大于上一级`);
+        return;
+      }
+    }
+    setSaving(true);
+    try {
+      const res = await apiUpdateSiteSettings({ levels: form, levels_fx: fx });
+      const defs = cloneDefs(res.levels);
+      setForm(defs);
+      setSaved(defs);
+      setSavedFx(fx);
+      toast("等级配置已保存", "ok");
+    } catch (e) {
+      toast(e instanceof Error ? e.message : "保存失败");
+    } finally {
+      setSaving(false);
+    }
+  };
+
+  // 重置：仅回填默认等级表（2–12 约束内），需再点保存才生效
+  const resetToDefault = () => {
+    if (!form) return;
+    setForm(cloneDefs(DEFAULT_LEVEL_DEFS));
+    setResetOpen(false);
+    toast("已恢复默认等级表，点击保存生效", "ok");
+  };
+
+  return (
+    <div className="admin-settings-stack">
+      <div>
+        <h2 className="text-lg font-bold" style={{ color: "var(--ink)" }}>
+          等级管理
+        </h2>
+        <p className="meta text-sm mt-1">
+          用户等级由累计获得积分决定，达到某级阈值即晋升。可配置等级数量（2–{MAX_LEVEL_COUNT}{" "}
+          级）、每级所需积分与配色；等级徽章仅显示 Lv.n，不弹悬浮提示。
+        </p>
+      </div>
+
+      {!form ? (
+        <p className="meta px-1 py-6">加载等级配置…</p>
+      ) : form.length === 0 ? (
+        <div className="panel text-center py-12">
+          <p className="meta">等级配置加载失败，请刷新页面重试。</p>
+        </div>
+      ) : (
+        <div className="panel p-0 overflow-hidden">
+          {form.map((d, i) => {
+            const n = i + 1;
+            const tokens = LEVEL_COLOR_TOKENS[d.color] ?? LEVEL_COLOR_TOKENS.neutral;
+            const textBg = splitBackground(tokens.text ?? "none");
+            const isLast = i === form.length - 1;
+            return (
+              <div
+                key={n}
+                className="flex items-center gap-4 px-4 py-3 flex-wrap"
+                style={{ borderTop: i === 0 ? "none" : "1px solid var(--line)" }}
+              >
+                {/* 预览：与 LevelBadge 同构（外层底色 + .lv-text 文字层），实时反映未保存的修改 */}
+                <span className="w-14 shrink-0 flex">
+                  <span
+                    className={LEVEL_BADGE_CLASS}
+                    style={{
+                      background: tokens.bg,
+                      boxShadow: `inset 0 0 0 1px ${tokens.ring ?? "transparent"}`,
+                    }}
+                  >
+                    <span
+                      className="lv-text"
+                      style={{
+                        backgroundImage: textBg.image,
+                        backgroundPosition: textBg.position,
+                        backgroundSize: textBg.size,
+                        backgroundClip: "text",
+                        WebkitBackgroundClip: "text",
+                        color: tokens.fg,
+                      }}
+                    >
+                      Lv.{n}
+                    </span>
+                  </span>
+                </span>
+                <div className="shrink-0">
+                  <p className="text-xs mb-1" style={{ color: "var(--ink-2)" }}>
+                    所需累计积分
+                  </p>
+                  <AdminStepper
+                    value={d.threshold}
+                    onChange={(v) => setThreshold(i, v)}
+                    min={0}
+                    max={1000000}
+                    unit="分"
+                    ariaLabel={`Lv.${n} 所需积分`}
+                    disabled={saving || n === 1}
+                  />
+                </div>
+                <div className="min-w-0">
+                  <p className="text-xs mb-1.5" style={{ color: "var(--ink-2)" }}>
+                    配色（前景/背景）
+                  </p>
+                  <div className="flex gap-1.5 flex-wrap">
+                    {LEVEL_COLOR_KEYS.map((c) => {
+                      const t = LEVEL_COLOR_TOKENS[c];
+                      const active = d.color === c;
+                      return (
+                        <button
+                          key={c}
+                          type="button"
+                          aria-label={c}
+                          title={c}
+                          disabled={saving}
+                          onClick={() => setColor(i, c)}
+                          className="w-6 h-6 rounded-full transition-transform"
+                          style={{
+                            background: t.bg,
+                            outline: active
+                              ? "2px solid var(--ink)"
+                              : "1px solid var(--line)",
+                            outlineOffset: 1,
+                          }}
+                        />
+                      );
+                    })}
+                  </div>
+                </div>
+                <span className="flex-1" />
+                {isLast && (
+                  <button
+                    type="button"
+                    className="btn btn-line btn-sm shrink-0"
+                    style={{ color: "var(--danger)" }}
+                    disabled={saving || form.length <= 2}
+                    onClick={removeLast}
+                  >
+                    <Trash2 size={13} /> 删除此级
+                  </button>
+                )}
+              </div>
+            );
+          })}
+          {/* 添加新等级：整宽虚线条目，与上方项同宽 */}
+          {form.length < MAX_LEVEL_COUNT ? (
+            <button
+              type="button"
+              className="w-full flex items-center justify-center gap-1.5 py-3.5 text-sm transition-colors hover:opacity-80"
+              style={{
+                borderTop: "1.5px dashed var(--line)",
+                color: "var(--ink-2)",
+              }}
+              disabled={saving}
+              onClick={addLevel}
+            >
+              <Plus size={15} /> 添加新等级
+            </button>
+          ) : (
+            <div
+              className="w-full flex items-center justify-center py-3.5 text-xs"
+              style={{
+                borderTop: "1.5px dashed var(--line)",
+                color: "var(--ink-3)",
+              }}
+            >
+              已达 {MAX_LEVEL_COUNT} 级上限
+            </div>
+          )}
+        </div>
+      )}
+
+      <div className="flex items-center gap-4 flex-wrap">
+        <button
+          type="button"
+          className="btn btn-primary btn-sm"
+          disabled={saving || !dirty}
+          onClick={() => void save()}
+        >
+          {saving ? "保存中…" : "保存等级配置"}
+        </button>
+        <button
+          type="button"
+          className="btn btn-line btn-sm"
+          disabled={saving || !form}
+          onClick={() => setResetOpen(true)}
+        >
+          <RotateCcw size={13} /> 重置
+        </button>
+        <div className="flex items-center gap-2">
+          <AdminSwitch
+            checked={fx}
+            disabled={saving}
+            onChange={() => setFx((v) => !v)}
+            label="特效动画"
+          />
+        </div>
+        <span className="admin-settings-instant">
+          {dirty
+            ? "有未保存的修改"
+            : "已保存的配色在页面刷新后生效，等级数值即时按新阈值重算"}
+        </span>
+      </div>
+
+      <ConfirmDialog
+        open={resetOpen}
+        title="重置等级配置"
+        message={`将恢复为默认 ${DEFAULT_LEVEL_DEFS.length} 级配置（当前修改不会立即生效，需再点击保存）。确定重置？`}
+        confirmLabel="重置"
+        danger
+        onCancel={() => setResetOpen(false)}
+        onConfirm={resetToDefault}
+      />
+
+      <ConfirmDialog
+        open={leave.leaveOpen}
+        title="有未保存的修改"
+        message="离开后，当前尚未保存的等级配置修改会丢失。确定离开？"
+        confirmLabel="离开"
+        danger
+        onCancel={leave.cancelLeave}
+        onConfirm={leave.confirmLeave}
+      />
+    </div>
+  );
+}