fix(a11y): every side-panel pin names its panel; the tab under an open card leaves the tree

The card's own pin and the drawer's still said 'Unpin panel' / 'Pin panel open' after the edge tab
learned the title (F6). Naming them too made two buttons share a name, because the invisible tab
under an open card was still in the accessibility tree: it is now aria-hidden as well as out of
the Tab order. The generic sidebar.pin / unpin keys are gone.

frontend/src/i18n/locales/en/sidebar.json

@@ -10,8 +10,6 @@
   "hideWidget": "Hide widget",
   "expand": "Expand",
   "collapse": "Collapse",
-  "pin": "Pin panel open",
-  "unpin": "Unpin panel",
   "pinNamed": "Pin {{title}} open",
   "unpinNamed": "Unpin {{title}}",
   "openPanel": "Open {{title}}",

frontend/src/i18n/locales/hu/sidebar.json

@@ -10,8 +10,6 @@
   "hideWidget": "Modul elrejtése",
   "expand": "Kibontás",
   "collapse": "Összecsukás",
-  "pin": "Panel rögzítése nyitva",
-  "unpin": "Panel rögzítésének feloldása",
   "pinNamed": "{{title}} rögzítése nyitva",
   "unpinNamed": "{{title}} rögzítésének feloldása",
   "openPanel": "{{title}} megnyitása",