feat: add employee management, backend health check, and UI improvements

server/src/app/models/employee_change_log.py

@@ -0,0 +1,21 @@
+from __future__ import annotations
+
+import uuid
+from datetime import datetime
+
+from sqlalchemy import DateTime, ForeignKey, String
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from app.db.base_class import Base
+
+
+class EmployeeChangeLog(Base):
+    __tablename__ = "employee_change_logs"
+
+    id: Mapped[str] = mapped_column(String(36), primary_key=True, default=lambda: str(uuid.uuid4()))
+    employee_id: Mapped[str] = mapped_column(ForeignKey("employees.id"), index=True)
+    action: Mapped[str] = mapped_column(String(255))
+    owner: Mapped[str] = mapped_column(String(100))
+    occurred_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), index=True)
+
+    employee = relationship("Employee", back_populates="change_logs")