Potential fixes for 2 code quality findings

backend/tests/fakes.py

@@ -323,7 +323,7 @@ def get_latest_for_assembly(self, assembly_id: uuid.UUID) -> SelectionRunRecord
         if not assembly_records:
             return None
         # Sort by created_at, return the most recent
-        return max(assembly_records, key=lambda r: r.created_at or "")
+        return max(assembly_records, key=lambda r: r.created_at or datetime.min)
 
     def get_running_tasks(self) -> Iterable[SelectionRunRecord]:
         """Get all currently running selection tasks."""
@@ -343,7 +343,7 @@ def get_by_assembly_id_paginated(
         # Get all records for the assembly
         all_records = sorted(
             [item for item in self._items if item.assembly_id == assembly_id],
-            key=lambda r: r.created_at or "",
+            key=lambda r: r.created_at or datetime.min,
             reverse=True,  # Newest first
         )
 
@@ -453,11 +453,11 @@ def get_by_token(self, token: str) -> EmailConfirmationToken | None:
 
     def count_recent_requests(self, user_id: uuid.UUID, since: datetime) -> int:
         """Count email confirmation requests for a user since a given datetime."""
-        count = 0
-        for item in self._items:
-            if item.user_id == user_id and item.created_at >= since:
-                count += 1
-        return count
+        return sum(
+            1
+            for item in self._items
+            if item.user_id == user_id and item.created_at >= since
+        )
 
     def delete_old_tokens(self, before: datetime) -> int:
         """Delete tokens created before a given datetime. Returns count deleted."""