feat: add sound effects, improved stroke recognition, instant locale switching with scramble text animation

- Add SoundManager with Web Audio API synthesized sounds (stroke error, drawing complete, session complete)
- Add sound effects toggle in settings (persisted via localStorage)
- Improve stroke recognition: curvature similarity, max point deviation, stroke length ratio checks
- Loosen thresholds for long strokes and first-stroke positioning
- Implement instant locale switching (no save required)
- Add ScrambleText component with character-by-character morphing animation
- Apply ScrambleText globally across all views, widgets, and dialogs
- Add i18n keys for sound effects settings (EN/DE/JA)

client/src/components/dashboard/WidgetHeatmap.vue

@@ -5,13 +5,15 @@
   )
     template(#header-right)
       .legend-container
-        span.text-caption.text-medium-emphasis.mr-1 {{ $t('stats.less') }}
+        span.text-caption.text-medium-emphasis.mr-1
+          ScrambleText(:text="$t('stats.less')")
         .legend-box.level-0
         .legend-box.level-1
         .legend-box.level-2
         .legend-box.level-3
         .legend-box.level-4
-        span.text-caption.text-medium-emphasis.ml-1 {{ $t('stats.more') }}
+        span.text-caption.text-medium-emphasis.ml-1
+          ScrambleText(:text="$t('stats.more')")
 
     .heatmap-container
       .heatmap-year
@@ -25,7 +27,8 @@
                 )
               .text-center
                 .font-weight-bold {{ formatDate(day.date) }}
-                div {{ $t('stats.reviewsCount', { count: day.count }) }}
+                div
+                  ScrambleText(:text="$t('stats.reviewsCount', { count: day.count })")
 </template>
 
 <script setup>