feat(db): add migrations for RBAC, diagnostic, messaging, attendance, leave, invitation codes

- 0011: RBAC role flags and seed data

- 0012: diagnostic grade_id

- 0013: message recall

- 0014: message templates

- 0015: group messages and message reports/blocks

- 0016: invitation codes

- 0017: draft device sync

- 0018: attendance status reason

- 0019: attendance warning thresholds

- 0020: leave requests

- 0021: attendance period

drizzle/0016_invitation_codes.sql

@@ -0,0 +1,19 @@
+-- audit-P2-3: 注册邀请码表（admin 批量生成，注册时校验 + 自动分配角色/班级）
+CREATE TABLE IF NOT EXISTS `invitation_codes` (
+  `id` serial PRIMARY KEY,
+  `code` varchar(64) NOT NULL,
+  `email` varchar(255),
+  `role` varchar(50) NOT NULL,
+  `class_id` varchar(128),
+  `notes` varchar(500),
+  `created_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
+  `created_by` varchar(128),
+  `expires_at` timestamp NULL,
+  `used_by` varchar(128),
+  `used_at` timestamp NULL,
+  UNIQUE KEY `invitation_codes_code_unique` (`code`)
+);
+
+CREATE INDEX `invitation_codes_code_idx` ON `invitation_codes`(`code`);
+CREATE INDEX `invitation_codes_email_idx` ON `invitation_codes`(`email`);
+CREATE INDEX `invitation_codes_used_by_idx` ON `invitation_codes`(`used_by`);