feat(templates): branded Plyr video player for demos with download protection

- BrandedVideoPlayer (plyr-react) plays template demo videos with FlatRender
  blue branding (Plyr CSS vars) and NO download control.
- Download protection: no download button, native controls replaced, underlying
  <video> gets controlsList="nodownload" + disablePictureInPicture, and the
  right-click context menu is blocked.
- Template detail page uses it; gallery hover-preview cards get the same
  nodownload / no-context-menu / no-PiP guards.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

package.json

@@ -37,6 +37,8 @@
     "lucide-react": "^1.16.0",
     "next": "14.2.35",
     "next-intl": "^4.12.0",
+    "plyr": "^3.7.8",
+    "plyr-react": "^5.3.0",
     "react": "^18",
     "react-dom": "^18",
     "react-hook-form": "^7.76.0",