feat(vocab): integrate fallback core patterns and enhance vocabulary display in VocabLessonView

- Added a new method in VocabService to merge core pattern glosses with fallback patterns, improving vocabulary clarity and consistency.
- Updated VocabLessonView to utilize the merged core patterns, ensuring a comprehensive vocabulary overview for users.
- Refactored vocabulary handling logic to enhance user experience during vocabulary lessons, including improved display of lesson vocabulary.

frontend/src/i18n/locales/en/socialnetwork.json

@@ -456,7 +456,9 @@
                 "vocabPrepStep2": "Go through the same items again (active review, not testing yet).",
                 "vocabPrepConfirm2": "Second pass done",
                 "vocabPrepReady": "You can start the vocabulary trainer now.",
+                "vocabOverviewToggle": "Show full overview of terms",
                 "vocabTrainerLockedHint": "Please confirm two preparation steps under “Preparation before the vocabulary trainer” first.",
+                "exerciseUnlockHintAfterPrep": "Work through the prepared terms first. The chapter test will unlock afterwards.",
                 "speakingTasks": "Speaking Tasks",
                 "speakingPrompt": "Speaking Prompt",
                 "practicalTasks": "Practical Tasks",