feat: bound Set Energy to a 4-20 keV placeholder range

Both Set Energy rows allowed 1-30 keV, an arbitrary spinbox default;
nothing downstream validates the request (daq.change_energy forwards
straight to bec). Shared ENERGY_MIN/MAX_KEV constants now bound both
spins to 4-20 keV with a tooltip flagging the range as pending
Beamline Scientist confirmation.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/unit/gui/test_data_collection_settings.py

@@ -351,6 +351,11 @@ def test_db_override_source_toggle_clears_pending(qapp, qtbot):
 
 
 def test_energy_spin_pending_until_change_energy(settings_panel):
+    # same placeholder limits as the Beamline setup row (shared constants)
+    assert settings_panel.energy_spin.minimum() == 4.0
+    assert settings_panel.energy_spin.maximum() == 20.0
+    assert "Beamline Scientist" in settings_panel.energy_spin.toolTip()
+
     box = settings_panel.energy_spin.lineEdit()
     settings_panel.energy_spin.setValue(12.4)
     assert box.property("movestate") == "pending"

tests/unit/gui/test_monochromator_panel.py

@@ -36,3 +36,13 @@ def test_fast_shutter_row(qtbot, daq_status_factory):
         panel.open_shutter_button.click()
     with qtbot.waitSignal(panel.close_shutter, timeout=1000):
         panel.close_shutter_button.click()
+
+
+def test_energy_spin_placeholder_limits(qtbot):
+    # 4-20 keV is a placeholder pending Beamline Scientist confirmation; the
+    # tooltip must say so because nothing downstream validates the request.
+    panel = MonochromatorPanel()
+    qtbot.addWidget(panel)
+    assert panel.energy_spin.minimum() == 4.0
+    assert panel.energy_spin.maximum() == 20.0
+    assert "Beamline Scientist" in panel.energy_spin.toolTip()