fix: i18n translations and annotation property changes on selected objects

- Complete English translation catalog (44 entries fixed/added)
- Fix Fabric.js Group cache invalidation (active.dirty = true) so color,
  thickness and line-dash changes are visible on selected markers/arrows
- Fix Italian .po placeholder mismatch (%(detail)s -> %(error)s)
- Bump annotation-editor.js cache buster to v8

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

client/templates/maker/task_drawing.html

@@ -353,7 +353,7 @@
 <script>
   pdfjsLib.GlobalWorkerOptions.workerSrc = 'https://cdnjs.cloudflare.com/ajax/libs/pdf.js/3.11.174/pdf.worker.min.js';
 </script>
-<script src="{{ url_for('static', filename='js/annotation-editor.js') }}?v=7"></script>
+<script src="{{ url_for('static', filename='js/annotation-editor.js') }}?v=8"></script>
 <script>
 function taskDrawing() {
   const taskData = window.__taskData || {};
@@ -372,19 +372,19 @@ function taskDrawing() {
     annoColor: '#2563EB',
     annoStrokeWidth: 2,
     colorOptions: [
-      { value: '#2563EB', label: 'Blu' },
-      { value: '#DC2626', label: 'Rosso' },
-      { value: '#16A34A', label: 'Verde' },
-      { value: '#F59E0B', label: 'Arancio' },
-      { value: '#8B5CF6', label: 'Viola' },
-      { value: '#000000', label: 'Nero' },
+      { value: '#2563EB', label: {{ _('Blu')|tojson }} },
+      { value: '#DC2626', label: {{ _('Rosso')|tojson }} },
+      { value: '#16A34A', label: {{ _('Verde')|tojson }} },
+      { value: '#F59E0B', label: {{ _('Arancio')|tojson }} },
+      { value: '#8B5CF6', label: {{ _('Viola')|tojson }} },
+      { value: '#000000', label: {{ _('Nero')|tojson }} },
     ],
     strokeOptions: [1, 2, 3, 4],
     annoLineDash: [],
     lineDashOptions: [
-      { value: [], label: 'Continua', icon: 'solid' },
-      { value: [8, 4], label: 'Tratteggiata', icon: 'dashed' },
-      { value: [3, 3], label: 'Punteggiata', icon: 'dotted' },
+      { value: [], label: {{ _('Continua')|tojson }}, icon: 'solid' },
+      { value: [8, 4], label: {{ _('Tratteggiata')|tojson }}, icon: 'dashed' },
+      { value: [3, 3], label: {{ _('Punteggiata')|tojson }}, icon: 'dotted' },
     ],
 
     // Save state