refactor(settings/providers): align with DS conventions

Two consistency wins from the screenshot/DS audit pass.

Sync icon button now renders DS::Button (variant: icon, size: sm)
instead of a hand-rolled `button_to`. Same component used by other
icon-only actions across the app (settings/profiles, layouts/imports).
Visual delta: 28×28 → 32×32 (DS sm size). Accept the +4px for
consistency. `event.stopPropagation()` still wired via the form opt
so the row's <details> doesn't toggle when the user clicks the
button.

Group heading now follows the established Sure section-label style
(`text-xs font-medium text-secondary uppercase`) used by
`_settings_nav` and the imports/categories surfaces. The previous
sentence-case `text-sm text-primary` was a one-off that didn't
match the rest of the app. Locale strings stay sentence-case;
uppercase comes from CSS `text-transform`. Tests updated to
case-insensitively match the rendered heading text.

app/views/settings/providers/_group_heading.html.erb

@@ -1,9 +1,9 @@
 <%# locals: (title:, count: nil, description: nil, anchor: nil) %>
 <%= tag.div id: anchor.presence, class: "flex items-baseline justify-between gap-3 mt-5 mb-1.5 px-1" do %>
-  <h2 class="text-sm font-medium text-primary flex items-baseline gap-2">
+  <h2 class="text-xs font-medium text-secondary uppercase flex items-baseline gap-2">
     <%= title %>
     <% if count %>
-      <span class="text-subdued font-normal tabular-nums">· <%= count %></span>
+      <span class="text-subdued font-normal normal-case tabular-nums">· <%= count %></span>
     <% end %>
   </h2>
   <% if description.present? %>

app/views/settings/providers/_sync_button.html.erb

@@ -1,12 +1,15 @@
 <%# locals: (provider_key:, last_synced_at: nil) %>
 <% recently_synced = last_synced_at.present? && last_synced_at > 60.seconds.ago %>
 <% button_label = recently_synced ? t("settings.providers.recently_synced") : t("settings.providers.sync_provider") %>
-<%= button_to sync_provider_settings_providers_path(provider_key: provider_key),
-              method: :post,
-              disabled: recently_synced,
-              title: button_label,
-              aria: { label: button_label },
-              class: "inline-flex items-center justify-center w-7 h-7 rounded-md text-secondary hover:text-primary hover:bg-alpha-black-50 transition-colors disabled:opacity-40 disabled:cursor-not-allowed",
-              form: { onclick: "event.stopPropagation()", class: "inline-flex" } do %>
-  <%= icon "refresh-cw", size: "sm", class: "!w-3.5 !h-3.5" %>
-<% end %>
+<%= render DS::Button.new(
+      variant: "icon",
+      size: "sm",
+      icon: "refresh-cw",
+      href: sync_provider_settings_providers_path(provider_key: provider_key),
+      method: :post,
+      disabled: recently_synced,
+      title: button_label,
+      aria: { label: button_label },
+      class: "disabled:opacity-40 disabled:cursor-not-allowed",
+      form: { onclick: "event.stopPropagation()", class: "inline-flex" }
+    ) %>

test/system/settings/providers_test.rb

@@ -36,8 +36,8 @@ class Settings::ProvidersTest < ApplicationSystemTestCase
     titles = all("details").map { |d| d.find("summary h3", match: :first).text.squish }
     assert_equal titles.sort_by(&:downcase), titles, "Connection panels should render alphabetically by title"
 
-    connections_heading = page.find(:xpath, "//h2[contains(normalize-space(), 'Your connections')]")
-    available_heading = page.find(:xpath, "//h2[contains(normalize-space(), 'Available')]")
+    connections_heading = page.find(:xpath, "//h2[contains(translate(normalize-space(), 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz'), 'your connections')]")
+    available_heading = page.find(:xpath, "//h2[contains(translate(normalize-space(), 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz'), 'available')]")
     connections_y = connections_heading.native.location.y
     available_y = available_heading.native.location.y
 
@@ -65,12 +65,12 @@ class Settings::ProvidersTest < ApplicationSystemTestCase
 
     visit settings_providers_path
 
-    connections_heading = find(:xpath, "//h2[contains(., 'Your connections')]")
+    connections_heading = find(:xpath, "//h2[contains(translate(., 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz'), 'your connections')]")
     normalized = connections_heading.text.squish
-    assert_match(/Your connections .*· \d+/, normalized)
+    assert_match(/Your connections .*· \d+/i, normalized)
 
     connections_y = connections_heading.native.location.y
-    available_heading = find(:xpath, "//h2[contains(., 'Available')]")
+    available_heading = find(:xpath, "//h2[contains(translate(., 'ABCDEFGHIJKLMNOPQRSTUVWXYZ', 'abcdefghijklmnopqrstuvwxyz'), 'available')]")
     available_y = available_heading.native.location.y
     simplefin_y = find("details", text: "SimpleFIN").native.location.y
 
@@ -86,8 +86,8 @@ class Settings::ProvidersTest < ApplicationSystemTestCase
 
     visit settings_providers_path
 
-    assert_selector "h2", text: /\AYour connections/
-    assert_no_selector "h2", text: /\AAction needed/
+    assert_selector "h2", text: /\AYour connections/i
+    assert_no_selector "h2", text: /\AAction needed/i
   end
 
   test "enable banking with expiring session appears in your connections and auto-opens" do
@@ -104,7 +104,7 @@ class Settings::ProvidersTest < ApplicationSystemTestCase
 
     visit settings_providers_path
 
-    assert_selector "h2", text: /\AYour connections/
+    assert_selector "h2", text: /\AYour connections/i
 
     # Auto-expanded warning sections hide compact meta behind `group-open:hidden`;
     # collapse once so the re-consent copy is visible again.