feat: add FastAPI backend with PostgreSQL and start script fixes

- Add server/ directory with FastAPI backend
- Fix server/start.sh to properly handle venv on Windows/Git Bash
- Add alembic migrations and pyproject.toml
- Add server tests

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

server/src/app/repositories/employee.py

@@ -0,0 +1,20 @@
+from sqlalchemy.orm import Session
+
+from app.models.employee import Employee
+
+
+class EmployeeRepository:
+    def __init__(self, db: Session) -> None:
+        self.db = db
+
+    def list(self) -> list[Employee]:
+        return self.db.query(Employee).order_by(Employee.created_at.desc()).all()
+
+    def get(self, employee_id: str) -> Employee | None:
+        return self.db.query(Employee).filter(Employee.id == employee_id).first()
+
+    def create(self, employee: Employee) -> Employee:
+        self.db.add(employee)
+        self.db.commit()
+        self.db.refresh(employee)
+        return employee