Add re-order, spotlight/focus, and auto-position-snapshots features

- HTML5 drag-and-drop reordering of strip participants (per-GM flag)
- Shift+click toggles spotlight focus on a participant (gold ring indicator)
- Escape exits focus mode
- Auto-save strip position on drag end + every 30s with viewport validation
- Reset strip position button in Director's Board
- French locale strings for reset button

lang/fr.json

@@ -79,7 +79,8 @@
         "avModeEnable": "Activer A/V",
         "avModeDisable": "Désactiver A/V",
         "avConfig": "Paramètres A/V...",
-        "avConfigTitle": "Ouvrir les paramètres du serveur A/V de Foundry (serveur de signalisation, LiveKit, etc.)"
+        "avConfigTitle": "Ouvrir les paramètres du serveur A/V de Foundry (serveur de signalisation, LiveKit, etc.)",
+        "resetStrip": "Réinitialiser la position de la barre"
       },
       "bulk": {
         "showAll": "Tout afficher",