feat(app): a note as one card, as before

A note is one card on the tinted ground: its title, its tags behind an
Add tags chip, a line, then its text. The app bar says only how saving
stands; its "Note in …" title goes.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MMm7usAo6q9ZZRoPkWjoxi
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

halkyon_learn_flutter/lib/l10n/app_en.arb

@@ -232,10 +232,6 @@
   "noteDeleteMessage": "This note will be removed from the studyset. You can undo this for a few seconds.",
   "noteDeleteConfirm": "Delete",
   "noteDeleted": "Note deleted",
-  "noteNewTitleFor": "New note in \"{title}\"",
-  "@noteNewTitleFor": {"placeholders": {"title": {"type": "String"}}},
-  "noteTitleFor": "Note in \"{title}\"",
-  "@noteTitleFor": {"placeholders": {"title": {"type": "String"}}},
   "noteTitleHint": "Title",
   "noteEditing": "Editing…",
   "noteSaving": "Saving…",
@@ -246,7 +242,7 @@
   "noteFieldBody": "Text",
   "noteKeepThis": "Keep this",
   "noteAddTags": "Add tags",
-  "noteTags": "Tags",
+  "noteEditTags": "Edit tags",
   "studysetFlashcardsEmpty": "No flashcards yet",
   "studysetFlashcardsEmptyHint": "Add some to start studying.",
   "studysetAddMaterial": "Add material",