feat: 初始化高校人事请假考勤技能 (process-leave-attendance-default)

基于 skill-template 脚手架开发，包含：
- 5 张业务表（教职工、请假政策、考勤日历、请假记录、假期余额）
- 请假核算引擎（扣薪计算、审批层级判定、年假抵扣）
- CLI 入口（import-employees / calculate-leave / render-html）
- HTML 审批与扣薪报告生成
- 示例数据与完整测试套件（295 tests passed）

scripts/db/connection.py

@@ -0,0 +1,54 @@
+"""SQLite 连接与请假考勤业务表幂等初始化。"""
+
+from __future__ import annotations
+
+import sqlite3
+
+from db.display_metadata import init_display_metadata
+from db.leave_display_metadata import seed_leave_display_metadata
+from db.schema import BUSINESS_TABLES, TABLE_DDL
+from db.timestamp_columns import init_updated_at_trigger
+from util.runtime_paths import get_db_path
+
+
+def get_conn() -> sqlite3.Connection:
+    return sqlite3.connect(get_db_path())
+
+
+def init_db() -> None:
+    conn = get_conn()
+    try:
+        cur = conn.cursor()
+        for table_name, ddl in TABLE_DDL:
+            cur.execute(ddl)
+            init_updated_at_trigger(cur, table_name)
+        cur.execute(
+            """
+            CREATE INDEX IF NOT EXISTS idx_leave_requests_employee
+            ON leave_requests(employee_id, status)
+            """
+        )
+        cur.execute(
+            """
+            CREATE INDEX IF NOT EXISTS idx_leave_balances_employee
+            ON leave_balances(employee_id, balance_type)
+            """
+        )
+        cur.execute(
+            """
+            CREATE INDEX IF NOT EXISTS idx_leave_policies_type
+            ON leave_policies(leave_type)
+            """
+        )
+        cur.execute(
+            """
+            CREATE INDEX IF NOT EXISTS idx_attendance_holidays_date
+            ON attendance_holidays(holiday_date)
+            """
+        )
+        init_display_metadata(cur)
+        seed_leave_display_metadata(cur)
+        _ = BUSINESS_TABLES
+        conn.commit()
+    finally:
+        conn.close()