feat(library): show playtime per platform on game detail

Hero and library card show the set total. Fall back to the
row's own minutes when the API sends no total.

public/i18n/en.json

@@ -796,6 +796,12 @@
     "OTHER_OWNERS_other": "{{count}} other owners",
     "SHOW_OWNERS": "Show who owns it"
   },
+  "PLATFORMS": {
+    "TITLE": "Playtime per platform",
+    "TOTAL": "Total",
+    "LAST_PLAYED": "Last played",
+    "NEVER": "never"
+  },
   "LINKS": {
     "ALSO_IN_LIBRARY": "Also in your library:",
     "SAME_AS": "Same game as...",