feat: add vocabulary browser with filters, audio playback, and example sentences

- Add Vocabularies page with searchable, level-grouped grid
- Implement multi-faceted filter system (word type, verb class, transitivity, reading ending, character count)
- Add male/female voice audio playback via WaniKani pronunciation data
- Display context sentences from WaniKani API
- Collapsible mnemonics section in detail modal
- Component kanji chips navigate to Collection with pre-filled search
- Vocabulary sync uses upsert to keep data fresh (audio, sentences, normalized POS)
- Add Vocabulary model, controller, service, and API route
- Add seed data with 28 vocabulary entries including transitive/intransitive verb pairs
- Full i18n support (EN, DE, JA) for all new UI elements

client/src/plugins/i18n.js

@@ -10,6 +10,7 @@ const messages = {
       dashboard: 'Dashboard',
       review: 'Review',
       collection: 'Collection',
+      vocabularies: 'Vocabularies',
       settings: 'Settings',
       sync: 'Sync',
       logout: 'Logout',
@@ -99,6 +100,8 @@ const messages = {
       items: 'Items',
       language: 'Language',
       drawingTolerance: 'Drawing Tolerance',
+      strokeStrictness: 'Stroke Strictness',
+      advanced: 'Advanced',
       strict: 'Strict',
       loose: 'Loose',
       save: 'Save & Close',
@@ -142,6 +145,32 @@ const messages = {
       startLesson: 'Start Lesson',
       redoLesson: 'Redo Lesson',
     },
+    vocabulary: {
+      searchLabel: 'Search Vocabulary...',
+      placeholder: "e.g. '大人', 'otona', 'adult'",
+      loading: 'Loading Vocabularies...',
+      noMatches: 'No matches found',
+      tryDifferent: 'Try searching for a different word or reading.',
+      levelHeader: 'LEVEL',
+      levelLabel: 'Level',
+      primary: 'Primary',
+      mnemonics: 'Mnemonics',
+      meaningMnemonic: 'Meaning Mnemonic',
+      readingMnemonic: 'Reading Mnemonic',
+      components: 'Component Kanji',
+      exampleSentences: 'Example Sentences',
+      filters: 'Filters',
+      filterType: 'Word Type',
+      filterVerbClass: 'Verb Class',
+      filterTransitivity: 'Transitivity',
+      filterEnding: 'Reading Ending',
+      filterLength: 'Character Count',
+      clearAll: 'Clear All',
+      matchCount: '{n} results',
+      listenMale: 'Male',
+      listenFemale: 'Female',
+      close: 'Close',
+    },
   },
   de: {
     common: {
@@ -152,6 +181,7 @@ const messages = {
       dashboard: 'Übersicht',
       review: 'Lernen',
       collection: 'Sammlung',
+      vocabularies: 'Vokabeln',
       settings: 'Einstellungen',
       sync: 'Sync',
       logout: 'Abmelden',
@@ -241,6 +271,8 @@ const messages = {
       items: 'Einträge',
       language: 'Sprache',
       drawingTolerance: 'Zeichentoleranz',
+      strokeStrictness: 'Strichgenauigkeit',
+      advanced: 'Erweitert',
       strict: 'Strikt',
       loose: 'Locker',
       save: 'Speichern & Schließen',
@@ -284,6 +316,32 @@ const messages = {
       startLesson: 'Lektion starten',
       redoLesson: 'Lektion wiederholen',
     },
+    vocabulary: {
+      searchLabel: 'Vokabel suchen...',
+      placeholder: "z.B. '大人', 'otona', 'Erwachsener'",
+      loading: 'Lade Vokabeln...',
+      noMatches: 'Keine Treffer',
+      tryDifferent: 'Versuche einen anderen Suchbegriff.',
+      levelHeader: 'STUFE',
+      levelLabel: 'Stufe',
+      primary: 'Primär',
+      mnemonics: 'Eselsbrücken',
+      meaningMnemonic: 'Bedeutungs-Eselsbrücke',
+      readingMnemonic: 'Lesungs-Eselsbrücke',
+      components: 'Kanji-Bestandteile',
+      exampleSentences: 'Beispielsätze',
+      filters: 'Filter',
+      filterType: 'Wortart',
+      filterVerbClass: 'Verbklasse',
+      filterTransitivity: 'Transitivität',
+      filterEnding: 'Lesung-Endung',
+      filterLength: 'Zeichenanzahl',
+      clearAll: 'Zurücksetzen',
+      matchCount: '{n} Ergebnisse',
+      listenMale: 'Männlich',
+      listenFemale: 'Weiblich',
+      close: 'Schließen',
+    },
   },
   ja: {
     common: {
@@ -294,6 +352,7 @@ const messages = {
       dashboard: 'ダッシュボード',
       review: '復習',
       collection: 'コレクション',
+      vocabularies: '単語',
       settings: '設定',
       sync: '同期',
       logout: 'ログアウト',
@@ -383,6 +442,8 @@ const messages = {
       items: '個',
       language: '言語 (Language)',
       drawingTolerance: '描画許容範囲',
+      strokeStrictness: '筆画の厳密さ',
+      advanced: '詳細設定',
       strict: '厳しい',
       loose: '甘い',
       save: '保存して閉じる',
@@ -426,6 +487,32 @@ const messages = {
       startLesson: 'レッスン開始',
       redoLesson: 'レッスンをやり直す',
     },
+    vocabulary: {
+      searchLabel: '単語を検索...',
+      placeholder: "例: '大人', 'おとな', 'adult'",
+      loading: '単語を読み込み中...',
+      noMatches: '見つかりませんでした',
+      tryDifferent: '別のキーワードで検索してください。',
+      levelHeader: 'レベル',
+      levelLabel: 'レベル',
+      primary: '主要',
+      mnemonics: '覚え方',
+      meaningMnemonic: '意味の覚え方',
+      readingMnemonic: '読みの覚え方',
+      components: '構成漢字',
+      exampleSentences: '例文',
+      filters: 'フィルター',
+      filterType: '品詞',
+      filterVerbClass: '動詞の種類',
+      filterTransitivity: '自他',
+      filterEnding: '読みの語尾',
+      filterLength: '文字数',
+      clearAll: 'クリア',
+      matchCount: '{n}件',
+      listenMale: '男性',
+      listenFemale: '女性',
+      close: '閉じる',
+    },
   },
 };