feat(skill&shield): 实现护盾持续时间功能，调整魔法盾冷却

1.  为护盾技能添加duration配置，支持永久/限时护盾
2.  新增护盾倒计时逻辑，到期自动清空护盾
3.  调整英雄6301魔法盾的冷却时间为10秒，新增7秒持续时长配置
4.  重构HeroAttrsComp，新增护盾持续时间字段与清空护盾方法

assets/script/game/common/config/SkillSet.ts

@@ -166,6 +166,7 @@ export interface SkillConfig {
     bck_chance?: number,       // 击退概率（百分点；未配置视为 0 不击退，可由 heroSet overrides 覆写）
     buff_type?: Attrs,         // Buff 类型 (单一职责)
     timed_buff_id?: number,    // 计时性 buff 配置 id（指向 BuffList），存在时走 buffManager 而非永久 add_*
+    shield_duration?: number,  // 护盾持续时间（秒），仅 kind=Shield 生效；缺省/<=0 表示永久护盾
     buff_value?: number,       // 覆写计时 buff 的修饰数值（modifiers.value / tick.damage_or_heal），由药水卡自定义档位
     buff_duration?: number,    // 覆写计时 buff 的持续时间（秒），不配置则用 BuffList 默认值
     buff_chance?: number,      // 计时 buff 施加概率（百分点，缺省 100）
@@ -205,6 +206,7 @@ export interface SkillOverrides {
     bck_chance?: number;
     buff_type?: Attrs;
     timed_buff_id?: number;
+    shield_duration?: number;
     buff_value?: number;
     buff_duration?: number;
     buff_chance?: number;
@@ -384,8 +386,8 @@ export const SkillSet: Record<number, SkillConfig> = {
     //============================= ======  辅助技能  回合技能 ====== ========================== 
     6301: {
         uuid: 6301, name: "护盾", sp_name: "buff_wind", icon: "28-Electric-Wave", TGroup: TGroup.Self, readyAnm: "up_blue", endAnm: "", act: "atk",
-        DTType: DTType.single, kind: SkillKind.Shield, ap: 30, hit_count: 1, hitcd: 0.2, speed: 720, with: 0, ready: 0.2, EAnm: 0, DAnm: "", IType: IType.support,
-        RType: RType.fixed, EType: EType.animationEnd, info: "获得施法者最大生命30%的护盾",
+        DTType: DTType.single, kind: SkillKind.Shield, ap: 30, hit_count: 1, hitcd: 0.2, speed: 720, with: 0, ready: 0.2, EAnm: 0, DAnm: "", IType: IType.support, shield_duration: 7,
+        RType: RType.fixed, EType: EType.animationEnd, info: "获得施法者最大生命30%的护盾, 持续7秒",
     },
     6302: {
         uuid: 6302, name: "治疗", sp_name: "buff_wind", icon: "g_priest_zldy_skill", TGroup: TGroup.Team, readyAnm: "up_green", endAnm: "", act: "atk",