feat: a round in the order cards come, shared daily limits, and a start screen

Studying:
- A round is one list in the order its cards come: those done, the one
  shown, those to come. A card due again within the day goes back in
  after 4 more cards when rated Bad, at the end otherwise, so the pills
  above the card follow it; the buttons say "in 4 cards", "at the end",
  "now" (round_order.dart).
- The studied studyset's daily limits hold for everything inside it
  together, as Anki's do for subdecks: twenty topics start 20 new cards
  a day in all, not 20 each.
- The study header's studyset name shows whole on hover or long press.
- The assistant's button sits at the lower left: in the Library across
  from Create studyset, in a studyset above its bar, and higher while
  studying, above the buttons that answer the card.

A studyset:
- Progress also counts the learning paths' steps done and lists the
  PDFs not read to their end, begun first, each opening the reader,
  across its topics (MaterialProgressCubit).
- Next up starts with studying for the exam while one is ahead: its
  reviews due and the new cards its pace leaves for the day.
- Learning paths tagged with a level count towards its automatic exam
  plan and offer it, as cards do.
- A step's first heading equal to its title is dropped on import and
  hidden in paths imported before.

Signing out, or a session the server ended, leads to a start screen
(GitHub, email, without an account, another instance) rather than a new
anonymous account; only the very first start makes one by itself.
Settings names the kind of account and its instance.

Also: the Watch screen reads the cards once for held words and their
progress; its ±10 s buttons tick as the navigation bar does; a map card
keeps its view as its caption changes and brings a picked region
towards the middle; an empty or failed library can be pulled to sync.

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/jellyfin/watch_screen_test.dart

@@ -506,7 +506,18 @@ void main() {
   });
 
   testWidgets('the player has play or pause with 10 seconds back and on '
-      'beside it, and where it is from 0:00 to its length', (tester) async {
+      'beside it, each a short tick where the device vibrates, and where it '
+      'is from 0:00 to its length', (tester) async {
+    final ticks = <Object?>[];
+    tester.binding.defaultBinaryMessenger.setMockMethodCallHandler(
+      SystemChannels.platform,
+      (call) async {
+        if (call.method == 'HapticFeedback.vibrate') {
+          ticks.add(call.arguments);
+        }
+        return null;
+      },
+    );
     await watch(tester);
     await playTo(tester, const Duration(minutes: 1));
     expect(find.text('1:00'), findsOneWidget);
@@ -519,6 +530,7 @@ void main() {
     await tester.tap(find.byTooltip('10 seconds back'));
     await tester.pumpAndSettle();
     expect(players.last!.state.value.position, const Duration(seconds: 50));
+    expect(ticks, List.filled(3, 'HapticFeedbackType.selectionClick'));
   });
 
   testWidgets("YouTube's keys work, the lines' too, and ? lists them", (