feat(app): tag, edit, delete and swipe cards while studying, with tidier session sheets

- Above every studied card (but a matching one): the PDF it came from,
  its tags on one line ("+2 tags" for the rest) or "Add tags", and a
  menu to tag, edit or delete it; the session follows (an edited card
  shows as saved, a deleted one leaves the round).
- On phones, a front/back or vocabulary card swiped right is rated
  Good, left Bad; it tilts over the colour it heads for, and springs
  back when let go early.
- The session's settings: "Settings", a 48 dp Save that warns mid-round
  ("Heads up!"), steppers in an outlined box ("20 / day", "5 / 50"),
  the order in an outlined dropdown, the chosen tags with the rest
  behind "Filter by tags" / "+3 more".
- A studyset's study options: Save above Reset to defaults, the
  description small, reviews a day in steps of 25.
- One stepper look everywhere (study, Pomodoro profiles), its buttons
  "Decrease" and "Increase".

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/test/feature/home/widget/home_screen_test.dart

@@ -74,7 +74,7 @@ void main() {
     await tester.pumpAndSettle();
     await tester.tap(find.text('Per week'));
     await tester.pump();
-    await tester.tap(find.byTooltip('More'));
+    await tester.tap(find.byTooltip('Increase'));
     await tester.pump();
     await tester.tap(find.text('Save goal'));
     await tester.pumpAndSettle();