Refactor backend to SQLModel; reset schema; add Company OS endpoints

backend/app/models/hr.py

@@ -0,0 +1,35 @@
+from __future__ import annotations
+
+from datetime import datetime
+
+from sqlmodel import Field, SQLModel
+
+
+class HeadcountRequest(SQLModel, table=True):
+    __tablename__ = "headcount_requests"
+
+    id: int | None = Field(default=None, primary_key=True)
+    department_id: int = Field(foreign_key="departments.id")
+    requested_by_manager_id: int = Field(foreign_key="employees.id")
+
+    role_title: str
+    employee_type: str  # human | agent
+    quantity: int = Field(default=1)
+
+    justification: str | None = None
+    status: str = Field(default="submitted")
+
+    created_at: datetime = Field(default_factory=datetime.utcnow)
+
+
+class EmploymentAction(SQLModel, table=True):
+    __tablename__ = "employment_actions"
+
+    id: int | None = Field(default=None, primary_key=True)
+    employee_id: int = Field(foreign_key="employees.id")
+    issued_by_employee_id: int = Field(foreign_key="employees.id")
+
+    action_type: str  # praise|warning|pip|termination
+    notes: str | None = None
+
+    created_at: datetime = Field(default_factory=datetime.utcnow)