feat(print-modal): show each printer slot's colour in the filament mapping (issue #3159)

The Print / Schedule dialog's filament mapping is where the colour a slice
asked for is compared against the colour actually loaded, and only the
left-hand side of that comparison had a swatch. The slot, and every slot in
its dropdown, was text -- and the text cannot be trusted: a slot's colour name
is resolved from the Color Catalog or, failing that, from hue, so a
third-party beige is announced as "Orange". A "Color mismatch" warning then
gives no way to tell a real mismatch from two names for the same hex without
opening the printer card in another tab, which on a farm swapping twenty or
thirty non-Bambu colours between machines is a check made many times a day.

Each slot now carries its colour and its hex, and the slot whose colour is
exactly the one the slice asked for is ticked. This works for a slot bound to
an inventory spool and for one configured through Configure Slot or on the
printer itself: the second kind has no inventory row behind it, and the
printer's own tray colour is then what draws. A bound spool contributes what a
tray record cannot -- SlotSpoolIdentity gains extra_colors and effect_type, so
a two-tone or glittery spool draws as itself rather than as its base colour.

The same treatment goes to the filament-override picker used for model-based
assignment. It is the same choice on the other dispatch path, and leaving it
text-only would have made one decision read two ways.

Both controls stop being <select>s to do it, because an <option> renders text
and nothing else. SlotPicker keeps what the select gave for free -- arrow,
Home/End, Enter and Escape keys, listbox semantics, and the border colouring
that encodes match, same-type-different-colour and not-loaded -- and is
portaled with position:fixed so it is not clipped by the dialog's own scroll
container, flipping above the row when there is no room below.

backend/tests/unit/services/test_filament_deficit.py

@@ -991,8 +991,52 @@ class TestSlotSpoolIdentity:
             # naming this slot from the hex is exactly the bug.
             "color_name": "Orange",
             "rgba": "FEC600FF",
+            # A plain single-colour spool: nothing extra to draw (#3159).
+            "extra_colors": None,
+            "effect_type": None,
         }
 
+    @pytest.mark.asyncio
+    async def test_internal_mode_carries_the_rest_of_the_colour(self, db_session, printer_factory):
+        """A tray record holds one hex, so the binding is the only source for the rest.
+
+        Without this the Print dialog's slot picker (#3159) draws a two-tone or
+        glittery spool as its base colour -- the one comparison the picker
+        exists to make, made against the wrong swatch.
+        """
+        from backend.app.services.filament_deficit import build_slot_materials
+
+        printer = await printer_factory(model="H2C")
+        spool = Spool(
+            brand="eSUN",
+            material="PLA",
+            subtype="Multicolor",
+            color_name="Rainbow",
+            rgba="FF0000FF",
+            extra_colors="00FF00,0000FF",
+            effect_type="Glitter",
+            label_weight=1000,
+            weight_used=0.0,
+        )
+        db_session.add(spool)
+        await db_session.commit()
+        await db_session.refresh(spool)
+        await _assign(db_session, printer_id=printer.id, spool_id=spool.id, ams_id=2, tray_id=0)
+
+        patches = TestFilamentDeficitBackupAware._patch_status(printer_id=printer.id, backup_on=False, model="H2C")
+        for p in patches:
+            p.start()
+        try:
+            slots = await build_slot_materials(db_session, printer.id)
+        finally:
+            for p in patches:
+                p.stop()
+
+        identity = slots[0].spool
+        assert identity is not None
+        assert identity.extra_colors == "00FF00,0000FF"
+        assert identity.effect_type == "Glitter"
+
     @pytest.mark.asyncio
     async def test_blank_fields_become_null_so_the_client_can_fall_back(self, db_session, printer_factory):
         """Per-field, not all-or-nothing: an unnamed colour still falls back to