feat(VocabPracticeDialog, VocabCourseView): implement SRS rating feature and enhance user feedback

- Added SRS rating buttons in VocabPracticeDialog to allow users to rate their confidence after answering vocabulary questions.
- Updated methods to handle SRS ratings and integrated them into the review process, improving spaced repetition feedback.
- Enhanced UI with new styles for SRS rating buttons and updated translations for SRS-related terms in multiple languages.
- Modified VocabCourseView to display appropriate introductory text based on SRS due items, improving user guidance.

frontend/src/views/social/VocabCourseView.vue

@@ -69,7 +69,9 @@
         <div v-if="todayRecommendedSteps.length > 0" class="course-today-plan">
           <h4 class="course-today-plan__title">{{ $t('socialnetwork.vocab.courses.courseTodayPlanTitle') }}</h4>
           <p class="course-today-plan__intro">
-            {{ dueReviewLessons.length > 0
+            {{ srsDueCount > 0
+              ? $t('socialnetwork.vocab.courses.courseTodayPlanIntroSrs')
+              : dueReviewLessons.length > 0
               ? $t('socialnetwork.vocab.courses.courseTodayPlanIntro')
               : $t('socialnetwork.vocab.courses.courseTodayPlanIntroNoDueReview') }}
           </p>