Fix get_all_users to fetch full KC representations and remove stale tests

KC 26+ does not return firstName/email from the paginated users list endpoint
regardless of briefRepresentation param. Switch to fetching each user's full
representation individually via GET /users/{id}, which always returns complete
data. This fixes the discrepancy scan showing false first_name/email mismatches
and the startup sync not populating last names.

Also remove two stale test_settings.py tests that validated default_billing_type,
which was removed as part of the billing_type cleanup.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/keycloak.py

@@ -345,23 +345,39 @@ class KeycloakClient:
         logger.info("Keycloak user deleted: %s", keycloak_id)
 
     def get_all_users(self) -> list[dict]:
-        """Paginated fetch of all realm users (full representation)."""
+        """Paginated fetch of all realm users (full representation).
+
+        KC 26+ may return brief representations from the list endpoint regardless
+        of the briefRepresentation param (firstName/email absent). We fetch each
+        user individually via GET /users/{id} which always returns full data.
+        """
         if not self.enabled:
             return []
 
-        all_users = []
+        # Page through to collect all user IDs
+        ids = []
         page_size = 100
         first = 0
         while True:
             resp = self._request(
-                "GET", "/users", params={"first": first, "max": page_size, "briefRepresentation": "false"}
+                "GET", "/users", params={"first": first, "max": page_size}
             )
             batch = resp.json()
-            all_users.extend(batch)
+            ids.extend(u["id"] for u in batch)
             if len(batch) < page_size:
                 break
             first += page_size
-        return all_users
+
+        # Fetch full representation for each user
+        full_users = []
+        for uid in ids:
+            try:
+                user = self.get_user(uid)
+                if user:
+                    full_users.append(user)
+            except KeycloakError:
+                pass
+        return full_users
 
     def get_all_groups(self) -> list[dict]:
         """Fetch all top-level groups."""

backend/tests/test_settings.py

@@ -283,19 +283,6 @@ class TestUpdateAllSettings:
         })
         assert resp.status_code == 400
 
-    def test_validates_default_billing_type(self, admin_client):
-        resp = admin_client.put("/api/settings/all", json={
-            "default_billing_type": "invalid_type",
-        })
-        assert resp.status_code == 400
-
-    def test_valid_billing_types(self, admin_client):
-        for bt in ("core", "collaborator", "standing"):
-            resp = admin_client.put("/api/settings/all", json={
-                "default_billing_type": bt,
-            })
-            assert resp.status_code == 200
-
     def test_validates_max_upload_size_mb(self, admin_client):
         resp = admin_client.put("/api/settings/all", json={
             "max_upload_size_mb": 0,