feat(providers): add status filter to providers dashboard

Adds a client-side status filter (All / Active / Inactive / No
connection) to the Providers page, applied over the already-fetched
provider + connection list. Status derives from getProviderStats
(total, allDisabled); noAuth providers count as Active. Filter composes
with the existing search across all provider sections. Part of #3699.

src/app/(dashboard)/dashboard/providers/utils.js

@@ -0,0 +1,19 @@
+export const STATUS_FILTER_OPTIONS = [
+  { value: "all", label: "All" },
+  { value: "active", label: "Active" },
+  { value: "inactive", label: "Inactive" },
+  { value: "none", label: "No connection" },
+];
+
+// noAuth providers (e.g. free proxies) are always usable even though they
+// never have a stored connection record, so they never fall into "none".
+export function getConnectionStatus(stats, isNoAuth = false) {
+  if (isNoAuth) return "active";
+  if (!stats || stats.total === 0) return "none";
+  return stats.allDisabled ? "inactive" : "active";
+}
+
+export function matchesStatusFilter(statusFilter, stats, isNoAuth = false) {
+  if (statusFilter === "all") return true;
+  return getConnectionStatus(stats, isNoAuth) === statusFilter;
+}