Show agent names on real estate dashboard charts (#23146)

Follow-up to the real estate demo app: the Agency Overview dashboard's
"Listings by agent" and "Showings by agent" bar charts grouped by the
agent relation, which rendered the agent's UUID on the axis.

Adding `primaryAxisGroupBySubFieldName: 'name.firstName'` groups by the
agent's first name instead, so the charts show agent names (Emma, Lucas,
Chloe, Louis).


<!-- This is an auto-generated description by cubic. -->
<a
href="https://cubic.dev/pr/twentyhq/twenty/pull/23146?utm_source=github"
target="_blank" rel="noopener noreferrer"
data-no-image-dialog="true"><picture><source
media="(prefers-color-scheme: dark)"
srcset="https://www.cubic.dev/buttons/review-in-cubic-dark.svg"><source
media="(prefers-color-scheme: light)"
srcset="https://www.cubic.dev/buttons/review-in-cubic-light.svg"><img
alt="Review in cubic"
src="https://www.cubic.dev/buttons/review-in-cubic-dark.svg"></picture></a>
<!-- End of auto-generated description by cubic. -->

packages/twenty-apps/internal/real-estate/src/page-layouts/agency-dashboard.page-layout.ts

@@ -169,6 +169,7 @@ export default definePageLayout({
             aggregateOperation: AggregateOperations.COUNT,
             primaryAxisGroupByFieldMetadataUniversalIdentifier:
               LISTING_AGENT_ON_PROPERTY_ID,
+            primaryAxisGroupBySubFieldName: 'name.firstName',
             ...BAR,
             primaryAxisOrderBy: 'VALUE_DESC',
           },
@@ -186,6 +187,7 @@ export default definePageLayout({
             aggregateOperation: AggregateOperations.COUNT,
             primaryAxisGroupByFieldMetadataUniversalIdentifier:
               AGENT_ON_SHOWING_ID,
+            primaryAxisGroupBySubFieldName: 'name.firstName',
             ...BAR,
             primaryAxisOrderBy: 'VALUE_DESC',
           },