feat(shields): add physical layouts and update keymap for Jiran

Add physical layouts and update the keymap for Ladniy's Jiran.
Layouts are added for all three possible transforms:
- Full (with additional pinky key and number row)
- Jian (with additional pinky key), re-uses Jian layout
- 6 column (Corne), re-uses Jian layout

Keymap update includes &studio_unlock.

app/boards/shields/jiran/layouts/position_map.dtsi

@@ -0,0 +1,7 @@
+/ {
+    layouts_ladniy_jiran_position_map: layouts_ladniy_jiran_position_map {
+        compatible = "zmk,physical-layout-position-map";
+
+        complete;
+    };
+};