feat(i18n): localize history item and story item dropdown menus

Covers the "..." action menu on both the History table (Play, Export
Audio, Export Package, Apply Effects, Regenerate, Delete) and on
individual story chat items (Play from here, Remove from Story).

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

app/src/i18n/locales/en/translation.json

@@ -104,6 +104,10 @@
       "title": "No items in this story",
       "hint": "Generate speech using the box below to add items"
     },
+    "itemActions": {
+      "playFromHere": "Play from here",
+      "removeFromStory": "Remove from Story"
+    },
     "toast": {
       "removeFailed": "Failed to remove item",
       "reorderFailed": "Failed to reorder items",
@@ -112,6 +116,14 @@
     }
   },
   "history": {
+    "actions": {
+      "menu": "Actions",
+      "play": "Play",
+      "exportAudio": "Export Audio",
+      "exportPackage": "Export Package",
+      "applyEffects": "Apply Effects",
+      "regenerate": "Regenerate"
+    },
     "deleteDialog": {
       "title": "Delete Generation",
       "body": "Are you sure you want to delete this generation from \"{{name}}\"? This action cannot be undone.",