homepage: pin Toolchain group to Toolchain tab

The task-board compose carries homepage.group=Toolchain. With no
matching entry in settings.yaml's layout: map, homepage placed it
on the default tab (Main) AND it appeared under the Toolchain tab,
producing duplicate cards. Declare the Toolchain group explicitly
with tab: Toolchain so it renders in exactly one place.

configs/homepage/settings.yaml

@@ -73,6 +73,11 @@ layout:
     tab: Infrastructure
     style: row
     columns: 4
+  Infra - IRV:
+    icon: mdi-brain
+    tab: Infrastructure
+    style: row
+    columns: 4
   Infra - ESH:
     icon: si-proxmox
     tab: Infrastructure
@@ -83,3 +88,8 @@ layout:
     tab: Toolchain
     style: row
     columns: 4
+  Toolchain:
+    icon: mdi-toolbox
+    tab: Toolchain
+    style: row
+    columns: 4