feat(savings): add "ONGOING · N" + "COMPLETED · N" section dividers

Same pattern as the bank-providers page's `AVAILABLE · 3` header (see
`app/views/settings/providers/_search_filters.html.erb` references):
small uppercase tracking-wide secondary label, separator dot, tabular
count. Replaces the prior "Completed · 1" inline label with a more
consistent treatment and adds an "Ongoing · N" header above the active
goals grid.

Name choice: "Ongoing" rather than "Active" because the grid includes
both `active` and `paused` AASM states; "ongoing" reads as still-in-
progress for both. Parallel to the existing "Completed" sibling.

config/locales/views/savings_goals/en.yml

@@ -20,6 +20,8 @@ en:
       goals_section:
         heading: Goals
         subtitle: Save toward what matters.
+      ongoing_section:
+        heading: Ongoing
       completed_section:
         heading: Completed
       search: