fix(savings_goals): update ONGOING count when filtering by status or search

The "ONGOING · N" badge was server-rendered with @active_goals.size and
never re-synced when the Stimulus filter hid cards. Add a count target
and update it alongside the existing empty/grid toggles.

app/javascript/controllers/savings_goals_filter_controller.js

@@ -5,7 +5,7 @@ import { Controller } from "@hotwired/stimulus";
 // and data-goal-status; the controller toggles `.hidden` on cards
 // based on the active query/chip.
 export default class extends Controller {
-  static targets = ["input", "chip", "card", "empty", "grid"];
+  static targets = ["input", "chip", "card", "empty", "grid", "count"];
   static values = { status: { type: String, default: "all" } };
 
   connect() {
@@ -35,6 +35,9 @@ export default class extends Controller {
     if (this.hasGridTarget) {
       this.gridTarget.classList.toggle("hidden", visible === 0);
     }
+    if (this.hasCountTarget) {
+      this.countTarget.textContent = visible;
+    }
   }
 
   selectChip(event) {