feat(jellyfin): an episode's own tag, and studying an episode's words

A word added from an episode gets the show's tag and the episode's own ("あかね噺 S1 E1"), hidden on cards. The words panel's Study button studies the studyset's cards of the video's words, on their schedules or crammed (each once): it pauses the video and first gives the episode's tag to the cards of its words the studyset held before, then opens the session on that tag. A study focus can now ask for cramming.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

halkyon_learn_flutter/lib/l10n/app_en.arb

@@ -2114,6 +2114,11 @@
   "@watchProgressLearned": {"placeholders": {"days": {"type": "int"}}},
   "watchJisho": "Look up on Jisho",
   "watchWider": "Longer words here",
+  "watchStudy": "Study",
+  "watchStudyWords": "Study this video's words",
+  "watchStudyNothing": "The studyset holds none of this video's words yet",
+  "watchStudyScheduled": "Study, on their schedules",
+  "watchStudyCram": "Cram, each once",
   "watchFilter": "Filter the words",
   "watchFilterFresh": "New words",
   "watchFilterHeld": "Words in the studyset",