deck contribution sprint 1: TableSeat.deck_variant FK + select_role wiring — TDD

- epic.TableSeat gains deck_variant FK → DeckVariant (nullable, SET_NULL)
- select_role view assigns request.user.equipped_deck to seat on role confirmation
- Migration 0006_add_deck_variant_to_tableseat
- ITs: test_select_role_assigns_equipped_deck_to_seat,
       test_select_role_no_deck_leaves_deck_variant_null

Code architected by Disco DeDisco <discodedisco@outlook.com>
Git commit message Co-Authored-By:
Claude Sonnet 4.6 <noreply@anthropic.com>

src/apps/epic/tests/integrated/test_views.py

@@ -680,6 +680,27 @@ class SelectRoleViewTest(TestCase):
             )
             mock_notify.assert_called_once_with(self.room.id)
 
+    def test_select_role_assigns_equipped_deck_to_seat(self):
+        earthman = DeckVariant.objects.get(slug="earthman")
+        self.founder.equipped_deck = earthman
+        self.founder.save(update_fields=["equipped_deck"])
+        self.client.post(
+            reverse("epic:select_role", kwargs={"room_id": self.room.id}),
+            data={"role": "PC"},
+        )
+        seat = TableSeat.objects.get(room=self.room, slot_number=1)
+        self.assertEqual(seat.deck_variant, earthman)
+
+    def test_select_role_no_deck_leaves_deck_variant_null(self):
+        self.founder.equipped_deck = None
+        self.founder.save(update_fields=["equipped_deck"])
+        self.client.post(
+            reverse("epic:select_role", kwargs={"room_id": self.room.id}),
+            data={"role": "PC"},
+        )
+        seat = TableSeat.objects.get(room=self.room, slot_number=1)
+        self.assertIsNone(seat.deck_variant)
+
     def test_select_role_requires_login(self):
         self.client.logout()
         response = self.client.post(