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

backend/model/level_test.go

@@ -0,0 +1,106 @@
+package model
+
+import "testing"
+
+// withLevelDefs 临时切换等级快照并在测试结束后恢复现场（快照为进程级全局态）
+func withLevelDefs(t *testing.T, defs []LevelDef) {
+	t.Helper()
+	prev := LevelDefs()
+	t.Cleanup(func() { ApplyLevelDefs(prev) })
+	ApplyLevelDefs(defs)
+}
+
+func TestLevelOfDefault(t *testing.T) {
+	withLevelDefs(t, DefaultLevelDefs())
+	cases := []struct {
+		total int
+		want  int
+	}{
+		{0, 1},
+		{49, 1},
+		{50, 2},
+		{51, 2},
+		{199, 2},
+		{200, 3},
+		{500, 4},
+		{1200, 5},
+		{3000, 6},
+		{7999, 6},
+		{8000, 7},
+		{1 << 30, 7},
+		{-5, 1},
+	}
+	for _, c := range cases {
+		if got := LevelOf(c.total); got != c.want {
+			t.Errorf("LevelOf(%d) = %d, want %d", c.total, got, c.want)
+		}
+	}
+}
+
+func TestLevelOfCustomConfig(t *testing.T) {
+	withLevelDefs(t, []LevelDef{
+		{Threshold: 0, Color: "neutral"},
+		{Threshold: 10, Color: "gold"},
+		{Threshold: 100, Color: "info"},
+	})
+	cases := []struct {
+		total int
+		want  int
+	}{
+		{0, 1},
+		{9, 1},
+		{10, 2},
+		{99, 2},
+		{100, 3},
+		{1 << 20, 3},
+	}
+	for _, c := range cases {
+		if got := LevelOf(c.total); got != c.want {
+			t.Errorf("LevelOf(%d) = %d, want %d", c.total, got, c.want)
+		}
+	}
+}
+
+func TestApplyLevelDefsFallback(t *testing.T) {
+	withLevelDefs(t, DefaultLevelDefs())
+	// 非法配置（首级阈值非 0、数量不足、非递增）一律回落默认表
+	invalid := [][]LevelDef{
+		{{Threshold: 10, Color: "gold"}, {Threshold: 50, Color: "info"}},
+		{{Threshold: 0, Color: "neutral"}},
+		{{Threshold: 0, Color: "neutral"}, {Threshold: 50, Color: "info"}, {Threshold: 50, Color: "ok"}},
+		{{Threshold: 0, Color: "neutral"}, {Threshold: -1, Color: "info"}},
+	}
+	for _, defs := range invalid {
+		ApplyLevelDefs(defs)
+		got := LevelDefs()
+		if len(got) != len(DefaultLevelDefs()) {
+			t.Fatalf("ApplyLevelDefs(invalid) 未回落默认表: got %d levels", len(got))
+		}
+	}
+}
+
+func TestValidLevelDefs(t *testing.T) {
+	valid := []LevelDef{{Threshold: 0, Color: "neutral"}, {Threshold: 1, Color: "gold"}}
+	if !ValidLevelDefs(valid) {
+		t.Errorf("ValidLevelDefs(合法两极) = false")
+	}
+	tooMany := make([]LevelDef, MaxLevelCount+1)
+	for i := range tooMany {
+		tooMany[i] = LevelDef{Threshold: i, Color: "gold"}
+	}
+	if ValidLevelDefs(tooMany) {
+		t.Errorf("ValidLevelDefs(超上限) = true")
+	}
+}
+
+func TestLevelDefsBoundaryCount(t *testing.T) {
+	withLevelDefs(t, DefaultLevelDefs())
+	defs := make([]LevelDef, MaxLevelCount)
+	for i := range defs {
+		defs[i] = LevelDef{Threshold: i * 10, Color: "gold"}
+	}
+	ApplyLevelDefs(defs)
+	if got := LevelOf(1 << 30); got != MaxLevelCount {
+		t.Errorf("LevelOf(极大值) = %d, want %d", got, MaxLevelCount)
+	}
+}