chore(pm): vendor the Aramesh/PM platform under pm/ (squash of Aramesh/PM @ 91f3271)

The PM panel (PmPanelPage -> iframe /pm/) needs the project-management
platform served at /pm/ on the ERP domain. Source: org repo Aramesh/PM,
branch feature/project-management-platform. Update via:
git subtree pull --prefix=pm aramesh-pm feature/project-management-platform --squash

pm/backend/tests/test_api_gantt_scheduling.py

@@ -0,0 +1,94 @@
+import pytest
+from httpx import ASGITransport, AsyncClient
+from sqlalchemy.ext.asyncio import AsyncSession, create_async_engine
+from sqlalchemy.orm import sessionmaker
+
+from app.db import get_db
+from app.main import app
+from app.models import Base, PMUser, Project, Task
+from app.security import create_token, hash_password
+
+
+@pytest.fixture
+def anyio_backend():
+    return "asyncio"
+
+
+@pytest.mark.asyncio
+async def test_gantt_and_relations_api():
+    engine = create_async_engine("sqlite+aiosqlite:///:memory:", echo=False)
+    async with engine.begin() as conn:
+        await conn.run_sync(Base.metadata.create_all)
+
+    async_session = sessionmaker(engine, class_=AsyncSession, expire_on_commit=False)
+
+    async with async_session() as session:
+        admin = PMUser(
+            username="admin",
+            password_hash=hash_password("admin123"),
+            display_name="مدیر ارشد",
+            role="project_manager",
+        )
+        session.add(admin)
+        await session.flush()
+
+        project = Project(name="پروژه تست گانت", description="تست")
+        session.add(project)
+        await session.flush()
+
+        task1 = Task(project_id=project.id, title="فونداسیون", duration=5)
+        task2 = Task(project_id=project.id, title="اسکلت بتنی", duration=10)
+        session.add_all([task1, task2])
+        await session.commit()
+
+        admin_id = admin.id
+        p_id = str(project.id)
+        t1_id = str(task1.id)
+        t2_id = str(task2.id)
+
+    token = create_token(admin_id)
+    headers = {"Authorization": f"Bearer {token}"}
+
+    async def override_get_db():
+        async with async_session() as session:
+            yield session
+
+    app.dependency_overrides[get_db] = override_get_db
+
+    try:
+        transport = ASGITransport(app=app)
+        async with AsyncClient(transport=transport, base_url="http://test", headers=headers) as client:
+            # 1. Add relation: task1 -> task2 (FS + 2 days lag)
+            rel_res = await client.post(
+                f"/api/v1/projects/{p_id}/relations",
+                json={"from_task_id": t1_id, "to_task_id": t2_id, "relation_type": "FS", "lag_days": 2},
+            )
+            assert rel_res.status_code == 200
+            rel_data = rel_res.json()["data"]
+            assert rel_data["relation_type"] == "FS"
+            assert rel_data["lag_days"] == 2
+            rel_id = rel_data["id"]
+
+            # 2. Add reverse relation: task2 -> task1 (should detect cycle and reject with 400)
+            cycle_res = await client.post(
+                f"/api/v1/projects/{p_id}/relations",
+                json={"from_task_id": t2_id, "to_task_id": t1_id, "relation_type": "FS"},
+            )
+            assert cycle_res.status_code == 400
+            assert "چرخه" in cycle_res.json()["error"]["message"]
+
+            # 3. Query Gantt dataset
+            gantt_res = await client.get(f"/api/v1/projects/{p_id}/gantt")
+            assert gantt_res.status_code == 200
+            gantt_data = gantt_res.json()["data"]
+            assert len(gantt_data["tasks"]) == 2
+            assert len(gantt_data["relations"]) == 1
+            assert len(gantt_data["critical_path"]) >= 1
+
+            # 4. Delete relation
+            del_rel = await client.delete(f"/api/v1/projects/{p_id}/relations/{rel_id}")
+            assert del_rel.status_code == 200
+            assert del_rel.json()["data"]["deleted"] is True
+    finally:
+        app.dependency_overrides.clear()
+        await engine.dispose()