feat: add 7 new shift artwork assets and update game icons

Add new shift-themed artwork images (cat-on-tiger, flying-over-the-city,
japanese-road, octo-mecha, paris-in-rain, steampunk-sky-city, tiger-warrior)
and register them in shift-artwork.json. Update game-icons.png and .psd.

data/shift-artwork.json

@@ -101,6 +101,48 @@
       "name": "Steampunk Future City",
       "key": "steampunk-future-city",
       "path": "assets/images/shift/steampunk-future-city.png"
+    },
+    {
+      "id": "cat-on-tiger",
+      "name": "Cat on Tiger",
+      "key": "cat-on-tiger",
+      "path": "assets/images/shift/cat-on-tiger.png"
+    },
+    {
+      "id": "flying-over-the-city",
+      "name": "Flying Over the City",
+      "key": "flying-over-the-city",
+      "path": "assets/images/shift/flying-over-the-city.png"
+    },
+    {
+      "id": "japanese-road",
+      "name": "Japanese Road",
+      "key": "japanese-road",
+      "path": "assets/images/shift/japanese-road.png"
+    },
+    {
+      "id": "octo-mecha",
+      "name": "Octo Mecha",
+      "key": "octo-mecha",
+      "path": "assets/images/shift/octo-mecha.png"
+    },
+    {
+      "id": "paris-in-rain",
+      "name": "Paris in the Rain",
+      "key": "paris-in-rain",
+      "path": "assets/images/shift/paris-in-rain.png"
+    },
+    {
+      "id": "steampunk-sky-city",
+      "name": "Steampunk Sky City",
+      "key": "steampunk-sky-city",
+      "path": "assets/images/shift/steampunk-sky-city.png"
+    },
+    {
+      "id": "tiger-warrior",
+      "name": "Tiger Warrior",
+      "key": "tiger-warrior",
+      "path": "assets/images/shift/tiger-warrior.png"
     }
   ]
 }