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_scheduling_service.py

@@ -0,0 +1,64 @@
+import uuid
+from datetime import date
+from types import SimpleNamespace
+
+import pytest
+
+from app.scheduling_service import calculate_schedule, check_for_cycle
+
+
+def test_cycle_detection():
+    id_a = uuid.uuid4()
+    id_b = uuid.uuid4()
+    id_c = uuid.uuid4()
+
+    edges = [
+        (id_a, id_b),
+        (id_b, id_c),
+    ]
+
+    # Adding C -> A should detect cycle
+    assert check_for_cycle(edges, id_c, id_a) is True
+
+    # Adding A -> A (self-loop) should detect cycle
+    assert check_for_cycle(edges, id_a, id_a) is True
+
+    # Adding C -> D (new node) should not detect cycle
+    id_d = uuid.uuid4()
+    assert check_for_cycle(edges, id_c, id_d) is False
+
+
+def test_cpm_forward_and_backward_pass():
+    id_a = uuid.uuid4()
+    id_b = uuid.uuid4()
+    id_c = uuid.uuid4()
+
+    t_a = SimpleNamespace(id=id_a, duration=3, planned_start=date(2026, 1, 1), parent_id=None, progress=0)
+    t_b = SimpleNamespace(id=id_b, duration=4, planned_start=None, parent_id=None, progress=0)
+    t_c = SimpleNamespace(id=id_c, duration=2, planned_start=None, parent_id=None, progress=0)
+
+    # A (3d) -[FS + 1 lag]-> B (4d) -[FS + 0 lag]-> C (2d)
+    rel_ab = SimpleNamespace(from_task_id=id_a, to_task_id=id_b, relation_type="FS", lag_days=1)
+    rel_bc = SimpleNamespace(from_task_id=id_b, to_task_id=id_c, relation_type="FS", lag_days=0)
+
+    res = calculate_schedule([t_a, t_b, t_c], [rel_ab, rel_bc], project_start=date(2026, 1, 1))
+
+    sched = res["tasks_schedule"]
+
+    # Task A: 2026-01-01, duration 3 is a gap -> ends 2026-01-04
+    assert sched[id_a]["planned_start"] == date(2026, 1, 1)
+    assert sched[id_a]["planned_end"] == date(2026, 1, 4)
+
+    # Task B starts right after A finishes (Jan 4) plus 1 lag day = Jan 5
+    assert sched[id_b]["planned_start"] == date(2026, 1, 5)
+    # B: duration 4 gap -> Jan 5 + 4 = Jan 9
+    assert sched[id_b]["planned_end"] == date(2026, 1, 9)
+
+    # Task C starts Jan 9, duration 2 gap -> ends Jan 11
+    assert sched[id_c]["planned_start"] == date(2026, 1, 9)
+    assert sched[id_c]["planned_end"] == date(2026, 1, 11)
+
+    # All three are on critical path
+    assert id_a in res["critical_path"]
+    assert id_b in res["critical_path"]
+    assert id_c in res["critical_path"]