feat(app): card tiles: the front, the tags, the options

A studyset's cards list as bordered rows of one height showing the
front, the card's tags above it and a badge when devices changed it
differently; tapping opens the composer, "…" offers editing and
deleting (after asking).

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

@@ -248,6 +248,12 @@
   "matchingRemoveItem": "Remove item",
   "matchingMinItems": "At least two items required",
 
+  "cardTileOptions": "Options",
+  "cardTileEdit": "Edit",
+  "cardTileDelete": "Delete",
+  "cardTileUntitled": "Untitled",
+  "cardTileConflict": "Changed on two devices",
+
   "commonCancel": "Cancel",
   "commonClose": "Close",
   "commonUndo": "Undo",