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/i18n/locales/en/socialnetwork.json

@@ -453,7 +453,16 @@
                 "acceptable": "Acceptable answers:",
                 "stats": "Stats",
                 "success": "Success",
-                "fail": "Fail"
+                "fail": "Fail",
+                "srsRateTitle": "How solid did it feel?",
+                "srsAgain": "Again",
+                "srsAgainHint": "repeat very soon",
+                "srsHard": "Hard",
+                "srsHardHint": "short interval",
+                "srsGood": "Good",
+                "srsGoodHint": "normal schedule",
+                "srsEasy": "Easy",
+                "srsEasyHint": "longer interval"
             },
             "search": {
                 "open": "Search",
@@ -813,7 +822,8 @@
                 "srsEyebrow": "Long-term memory",
                 "srsTitle": "{count} terms are due today",
                 "srsIntro": "This review comes from the SRS schedule of individual terms. It should come before new material because it stabilizes items close to forgetting.",
-                "srsStart": "Start daily review"
+                "srsStart": "Start daily review",
+                "courseTodayPlanIntroSrs": "Pedagogical order: start with the due SRS daily review for individual terms. Then quick reviews, block progress, and intensive review if needed. This stabilizes old material before new material is added."
             }
         }
     }