feat(push-notifications): 新增挑战提醒定时推送功能

新增每日定时推送系统，根据用户参与状态发送不同类型的挑战提醒：
- 已参与用户：每日发送鼓励推送
- 未参与用户：隔天发送挑战邀请
- 匿名用户：隔天发送通用邀请

包含推送历史记录表、定时任务调度、多类型文案模板和防重复发送机制

src/push-notifications/models/push-reminder-history.model.ts

@@ -0,0 +1,83 @@
+import { Table, Column, Model, DataType, Index } from 'sequelize-typescript';
+
+export enum ReminderType {
+  CHALLENGE_ENCOURAGEMENT = 'challenge_encouragement', // 已参与挑战用户的鼓励推送
+  CHALLENGE_INVITATION = 'challenge_invitation',       // 未参与挑战用户的邀请推送
+  GENERAL_INVITATION = 'general_invitation',           // 无userId用户的通用邀请
+}
+
+@Table({
+  tableName: 't_push_reminder_history',
+  underscored: true,
+})
+export class PushReminderHistory extends Model {
+  @Column({
+    type: DataType.UUID,
+    defaultValue: DataType.UUIDV4,
+    primaryKey: true,
+  })
+  declare id: string;
+
+  @Column({
+    type: DataType.STRING,
+    allowNull: true,
+    comment: '用户ID，可能为空',
+  })
+  declare userId: string | null;
+
+  @Column({
+    type: DataType.STRING,
+    allowNull: false,
+    comment: '设备推送令牌',
+  })
+  declare deviceToken: string;
+
+  @Column({
+    type: DataType.ENUM(...Object.values(ReminderType)),
+    allowNull: false,
+    comment: '提醒类型',
+  })
+  declare reminderType: ReminderType;
+
+  @Column({
+    type: DataType.DATE,
+    allowNull: false,
+    comment: '最后发送时间',
+  })
+  declare lastSentAt: Date;
+
+  @Column({
+    type: DataType.INTEGER,
+    allowNull: false,
+    defaultValue: 0,
+    comment: '发送次数',
+  })
+  declare sentCount: number;
+
+  @Column({
+    type: DataType.DATE,
+    allowNull: true,
+    comment: '下次可发送时间',
+  })
+  declare nextAvailableAt: Date | null;
+
+  @Column({
+    type: DataType.BOOLEAN,
+    allowNull: false,
+    defaultValue: true,
+    comment: '是否激活',
+  })
+  declare isActive: boolean;
+
+  @Column({
+    type: DataType.DATE,
+    defaultValue: DataType.NOW,
+  })
+  declare createdAt: Date;
+
+  @Column({
+    type: DataType.DATE,
+    defaultValue: DataType.NOW,
+  })
+  declare updatedAt: Date;
+}