feat(board-header): show subtitle on /all view

Add all_subtitle copy and render it in the board header when browsing
the aggregated all-directories feed.

src/components/board-header/__tests__/board-header.test.tsx

@@ -169,6 +169,7 @@ describe('BoardHeader', () => {
     expect(container.textContent).toContain('/all/ - All 5chan Directories');
     expect(container.querySelector('img')?.getAttribute('src')).toBe('banner-a.png');
     expect(container.textContent).not.toContain('subscriptions_subtitle');
+    expect(container.textContent).toContain('all_subtitle');
   });
 
   it('renders a clickable subscriptions subtitle that navigates to subscription settings', async () => {

src/components/board-header/board-header.tsx

@@ -83,7 +83,7 @@ const BoardHeader = () => {
         ? '/mod/ - Boards You Moderate'
         : defaultCommunity?.title || stableCommunity?.title;
   const subtitle = isInAllView
-    ? ''
+    ? t('all_subtitle')
     : isInSubscriptionsView
       ? subscriptionsSubtitle
       : isInModView
@@ -124,9 +124,9 @@ const BoardHeader = () => {
           >
             {subtitle}
           </button>
-        ) : isInDirectoryListView ? (
+        ) : isInDirectoryListView || isInAllView ? (
           <span>{subtitle}</span>
-        ) : !isInAllView && !isInModView && subtitle ? (
+        ) : !isInModView && subtitle ? (
           <span title={t('board_address_tooltip')}>{subtitle}</span>
         ) : (
           subtitle