feat(study): limits switch on and off, step by 5, and take any number typed

Your calls (2026-10-11): a switch per limit, and steps of 5 with any
number typed.

- A daily limit (new cards, reviews; in a studyset's study options and the
  study settings) is a switch, "Limit new cards per day", and its number
  while on. Counting down to 0 for no limit had to be guessed, and a goal
  has nothing like it. Switched off and on again, the limit comes back as
  it was; the first time, at the defaults' 20 new cards, or 200 reviews as
  Anki starts them. Stored as before: 0 still stands for none.
- The study goal counts in steps of 5 as the limits do (reviews: 25).
  Plus and minus go to the next multiple, so 12 steps to 15 or 10, never
  below the first step.
- Tapping the number lets any other be typed, from 1 (CountStepper.onTyped).

Pomodoro minutes and cards per round keep their own steps.

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_localizations.dart

@@ -5218,6 +5218,24 @@ abstract class AppLocalizations {
   /// **'Increase'**
   String get studyMore;
 
+  /// No description provided for @countStepperType.
+  ///
+  /// In en, this message translates to:
+  /// **'Type a number'**
+  String get countStepperType;
+
+  /// No description provided for @studyLimitNewPerDay.
+  ///
+  /// In en, this message translates to:
+  /// **'Limit new cards per day'**
+  String get studyLimitNewPerDay;
+
+  /// No description provided for @studyLimitReviewsPerDay.
+  ///
+  /// In en, this message translates to:
+  /// **'Limit reviews per day'**
+  String get studyLimitReviewsPerDay;
+
   /// No description provided for @studysetMenuReset.
   ///
   /// In en, this message translates to: