Map the tips payload onto the shape the client declares

Tips rendered as blank cards with unresolved placeholder text in their
accessibility labels. getTips was the one entity fetch in the client with no
translation from the wire's snake_case, so every tip arrived without the key
that selects its title and body, and the lookup silently missed.

The mapper now matches its siblings in that file. A test drives a card through
all eleven message keys the tips engine emits, so a twelfth added later fails
loudly instead of rendering an empty card, and two older tests that stubbed the
tips response as an empty object rather than an empty list have been corrected.

frontend/src/services/api.ts

@@ -205,6 +205,22 @@ function toPlannedLeaveDay(raw: RawPlannedLeaveDay): PlannedLeaveDay {
   }
 }
 
+export interface RawTip {
+  id: string
+  severity: 'info' | 'warning' | 'action'
+  message_key: string
+  data: Record<string, unknown>
+}
+
+function toTip(raw: RawTip): Tip {
+  return {
+    id: raw.id,
+    severity: raw.severity,
+    messageKey: raw.message_key,
+    data: raw.data,
+  }
+}
+
 interface RawLeaveWish {
   id: string
   workspace_id: string
@@ -926,7 +942,8 @@ export async function removeWorkspaceParent(
 // ---------------------------------------------------------------------------
 
 export async function getTips(workspaceId: string): Promise<Tip[]> {
-  return apiFetch(`/tips/${workspaceId}`)
+  const raw = (await apiFetch(`/tips/${workspaceId}`)) as RawTip[]
+  return raw.map(toTip)
 }
 
 // ---------------------------------------------------------------------------