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

templates/roster-strip.hbs

@@ -51,7 +51,7 @@
       {{#each participants}}
         <li class="sp-strip__participant-item" role="listitem">
           {{!-- ParticipantAvatar (44×44px container) --}}
-          <button class="sp-participant-avatar sp-state-{{state}}{{#if hasPendingOp}} sp-state-pending{{/if}} sp-shape-{{../tileShape}}"
+          <button class="sp-participant-avatar sp-state-{{state}}{{#if hasPendingOp}} sp-state-pending{{/if}}{{#if isFocused}} sp-state-focused{{/if}} sp-shape-{{../tileShape}}"
                   data-user-id="{{userId}}"
                   data-action="open-popover"
                   role="button"