ML-169.8: reduce Stats mount sync queries to 3

Move 7 non-critical queries out of synchronous mount into assign_async
and start_async tasks with skeleton loading placeholders.

Only scalar badge counters (collection count, wishlist count, scrobble
count) remain synchronous. All async sections use <.async_result> with
loading and failed slots. Scrobble activity preserves LiveView streams
via handle_async. On-this-day date changes use AsyncResult.ok/2.

priv/gettext/default.pot

@@ -2591,3 +2591,13 @@ msgstr ""
 #, elixir-autogen, elixir-format
 msgid "Settings"
 msgstr ""
+
+#: lib/music_library_web/live/stats_live/index.ex
+#, elixir-autogen, elixir-format
+msgid "Could not load records on this day."
+msgstr ""
+
+#: lib/music_library_web/live/stats_live/index.ex
+#, elixir-autogen, elixir-format
+msgid "Loading…"
+msgstr ""

priv/gettext/en/LC_MESSAGES/default.po

@@ -2591,3 +2591,13 @@ msgstr ""
 #, elixir-autogen, elixir-format
 msgid "Settings"
 msgstr ""
+
+#: lib/music_library_web/live/stats_live/index.ex
+#, elixir-autogen, elixir-format, fuzzy
+msgid "Could not load records on this day."
+msgstr ""
+
+#: lib/music_library_web/live/stats_live/index.ex
+#, elixir-autogen, elixir-format
+msgid "Loading…"
+msgstr ""