feat(admin): 优化后台运维与任务管理

完善平台、基准模型、定价规则和实时负载的紧凑查询与滚动展示，并固定关键操作列。

新增管理员任务记录、批量计费结算和用户组限流、额度及模型权限维护能力，同时补充任务脱敏、查询索引与 OpenAPI 契约。

验证：pnpm openapi、Go 全量测试、pnpm lint、pnpm test、pnpm build、gofmt 与差异格式检查均通过。

apps/api/internal/httpapi/admin_task_handlers_test.go

@@ -0,0 +1,22 @@
+package httpapi
+
+import "testing"
+
+func TestParseAdminTaskSensitiveMode(t *testing.T) {
+	tests := []struct {
+		value    string
+		full     bool
+		accepted bool
+	}{
+		{value: "", full: false, accepted: true},
+		{value: "masked", full: false, accepted: true},
+		{value: "FULL", full: true, accepted: true},
+		{value: "invalid", full: false, accepted: false},
+	}
+	for _, test := range tests {
+		full, accepted := parseAdminTaskSensitiveMode(test.value)
+		if full != test.full || accepted != test.accepted {
+			t.Fatalf("parseAdminTaskSensitiveMode(%q)=(%v,%v), want (%v,%v)", test.value, full, accepted, test.full, test.accepted)
+		}
+	}
+}