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

backend/app/api/activities.py

@@ -0,0 +1,30 @@
+from __future__ import annotations
+
+import json
+
+from fastapi import APIRouter, Depends
+from sqlmodel import Session, select
+
+from app.db.session import get_session
+from app.models.activity import Activity
+
+router = APIRouter(prefix="/activities", tags=["activities"])
+
+
+@router.get("")
+def list_activities(limit: int = 50, session: Session = Depends(get_session)):
+    items = session.exec(select(Activity).order_by(Activity.id.desc()).limit(max(1, min(limit, 200)))).all()
+    out = []
+    for a in items:
+        out.append(
+            {
+                "id": a.id,
+                "actor_employee_id": a.actor_employee_id,
+                "entity_type": a.entity_type,
+                "entity_id": a.entity_id,
+                "verb": a.verb,
+                "payload": json.loads(a.payload_json) if a.payload_json else None,
+                "created_at": a.created_at,
+            }
+        )
+    return out