refactor(ui): one rule for resettable, role key and display name; an honest reset label

The card menu's reset read 'Clear watch progress' but also un-hides and un-watches; it now says so.
The resettable rule, the demo-first role key and the display-name fallback each lived in several
components tied by comments; they are shared helpers now, and the menu reuses the card's own
strings instead of duplicate keys.

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

@@ -22,12 +22,8 @@
   "noDescription": "No description",
   "menu": {
     "label": "Video",
-    "markWatched": "Mark watched",
     "unmarkWatched": "Mark unwatched",
-    "save": "Save for later",
     "unsave": "Remove from saved",
-    "hide": "Hide",
-    "unhide": "Unhide",
-    "reset": "Clear watch progress"
+    "reset": "Reset (clear progress and status)"
   }
 }

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

@@ -22,12 +22,8 @@
   "noDescription": "Nincs leírás",
   "menu": {
     "label": "Videó",
-    "markWatched": "Megnézettnek jelöl",
     "unmarkWatched": "Megnézés visszavonása",
-    "save": "Mentés későbbre",
     "unsave": "Törlés a mentettek közül",
-    "hide": "Elrejtés",
-    "unhide": "Megjelenítés",
-    "reset": "Nézési előzmény törlése"
+    "reset": "Alaphelyzet (előzmény és státusz törlése)"
   }
 }