fix(usage): align cleanup loop break conditions with candidate row count

The cleanup loop break condition used rows_affected() from the UPDATE
statement, but for rows that only had blob/audit refs (no inline
compressed body data), the UPDATE reported 0 affected rows. This caused
the loop to exit after the first batch, skipping the majority of
candidates.

Change the break condition in all 4 cleanup functions from:
  if cleaned == 0 || cleaned < batch_size
to:
  if rows.len() < batch_size

This ensures the loop continues as long as SELECT returns a full batch,
regardless of how many rows the UPDATE actually modified.

Affected functions:
- cleanup_usage_raw_body_fields
- cleanup_usage_compressed_body_fields
- cleanup_usage_header_fields
- cleanup_usage_stale_body_fields

crates/aether-data/src/repository/usage/postgres/cleanup.rs

@@ -683,7 +683,7 @@ async fn cleanup_usage_raw_body_fields(
             .rows_affected();
         let cleaned = usize::try_from(cleaned).unwrap_or(usize::MAX);
         total_cleaned += cleaned;
-        if cleaned == 0 || cleaned < batch_size {
+        if rows.len() < batch_size {
             break;
         }
     }
@@ -736,7 +736,7 @@ async fn cleanup_usage_compressed_body_fields(
             .map_err(postgres_error)?;
         let cleaned = usize::try_from(cleaned).unwrap_or(usize::MAX);
         total_cleaned += cleaned;
-        if cleaned == 0 || cleaned < batch_size {
+        if rows.len() < batch_size {
             break;
         }
     }
@@ -1143,7 +1143,7 @@ async fn cleanup_usage_header_fields(
             .map_err(postgres_error)?;
         let cleaned = usize::try_from(cleaned).unwrap_or(usize::MAX);
         total_cleaned += cleaned;
-        if cleaned == 0 || cleaned < batch_size {
+        if rows.len() < batch_size {
             break;
         }
     }
@@ -1213,7 +1213,7 @@ async fn cleanup_usage_stale_body_fields(
             .map_err(postgres_error)?;
         let cleaned = usize::try_from(cleaned).unwrap_or(usize::MAX);
         total_cleaned += cleaned;
-        if cleaned == 0 || cleaned < batch_size {
+        if rows.len() < batch_size {
             break;
         }
     }