fix(i18n): every label a screen reader or tooltip says is translated

- The Plex playlist rows' "reorder"/"remove", the Plex filter chip's "remove" and the player
  slider's "reset" were English literals; each now names its row or setting in HU/EN.
- The playlist show header's chevron had no accessible name; its decorative thumbnail button left
  the tab order.
- The opt-in Glass tuner panel was English only: every word is translated, and each slider's label
  now names its number box and range.
- New `local/literal-a11y-text` lint rule (with its contract test): a literal word in aria-label,
  title, placeholder, alt and the other spoken/shown attributes fails lint.

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

@@ -327,7 +327,9 @@
     "removeFailed": "Couldn't remove it from the playlist.",
     "renameFailed": "Couldn't rename the playlist.",
     "deleteFailed": "Couldn't delete the playlist.",
-    "reorderFailed": "Couldn't save the new order."
+    "reorderFailed": "Couldn't save the new order.",
+    "removeItem": "Remove “{{title}}” from the playlist",
+    "reorderItem": "Move “{{title}}”"
   },
   "people": {
     "count_one": "{{count}} title",