feat(iot): B10 iot_subsystem 表 + CRUD + Redis 设备计数聚合

- 新增 sql/iot/V2.0.2__iot_subsystem.sql（iot_project + iot_subsystem）
- 新增 server 模块 subsystem/ 下 DO + Mapper + Service + Controller + VO（7 端点）
- 新增 IotSubsystemDeviceCountRedisDAO（HINCRBY + rebuild + ApplicationReadyEvent 触发）
- api 模块 ErrorCodeConstants 新增子系统段（1-050-020-xxx）
- server 模块 RedisKeyConstants 新增 SUBSYSTEM_DEVCOUNT
- 测试：8 个单元用例全绿（mvn test IotSubsystemServiceImplTest）
- Known Pitfalls 落地：
  ⚠️ 评审 A4：UK(name, tenant_id, project_id, deleted) + 应用层 existsByNameAndProject 兜底 NULL
  ⚠️ 评审 A6：device-stats 走 Redis Hash，避免 GROUP BY
  ⚠️ 评审 A7：simple-list 权限码 iot:device:query，返回字段仅 id/name/code
  ⚠️ 删除校验：Redis 计数 > 0 抛 SUBSYSTEM_HAS_DEVICES
  ⚠️ Redis 重建：ApplicationReadyEvent + try/catch + log.warn 不阻塞启动

说明：iot_device 当前无 subsystem_id 列（rebuild 逻辑标 TODO B11），
待 B11 加列后启用 DB 重建查询。

Co-Authored-By: Claude Sonnet (B10 subagent) <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.7 (1M context, orchestrator) <noreply@anthropic.com>

sql/iot/V2.0.2__iot_subsystem.sql

@@ -0,0 +1,39 @@
+-- B10: iot_project + iot_subsystem 表创建
+-- 版本: V2.0.2
+
+CREATE TABLE IF NOT EXISTS iot_project (
+    id          BIGINT PRIMARY KEY AUTO_INCREMENT,
+    name        VARCHAR(128) NOT NULL,
+    description TEXT,
+    icon        VARCHAR(256),
+    status      TINYINT NOT NULL DEFAULT 1,
+    sort        INT DEFAULT 0,
+    tenant_id   BIGINT NOT NULL,
+    creator     VARCHAR(64),
+    create_time DATETIME DEFAULT CURRENT_TIMESTAMP,
+    updater     VARCHAR(64),
+    update_time DATETIME DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+    deleted     BIT NOT NULL DEFAULT b'0',
+    UNIQUE KEY uk_name (name, tenant_id, deleted)
+) COMMENT='项目（架构预留，本期不开放 API）';
+
+CREATE TABLE IF NOT EXISTS iot_subsystem (
+    id          BIGINT PRIMARY KEY AUTO_INCREMENT,
+    name        VARCHAR(128) NOT NULL,
+    code        VARCHAR(64) NOT NULL,
+    description TEXT,
+    icon        VARCHAR(256),
+    status      TINYINT NOT NULL DEFAULT 1,
+    sort        INT DEFAULT 0,
+    project_id  BIGINT COMMENT '预留（允许 NULL）',
+    config      JSON,
+    tenant_id   BIGINT NOT NULL,
+    creator     VARCHAR(64),
+    create_time DATETIME DEFAULT CURRENT_TIMESTAMP,
+    updater     VARCHAR(64),
+    update_time DATETIME DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+    deleted     BIT NOT NULL DEFAULT b'0',
+    -- 【评审 A4】加 project_id 维度，MySQL NULL 不参与 UK 唯一性 → 应用层兜底
+    UNIQUE KEY uk_name (name, tenant_id, project_id, deleted),
+    UNIQUE KEY uk_code (code, tenant_id, project_id, deleted)
+) COMMENT='子系统';