Add video card insert feature + MkDocs video hydration + fixes

- New video card block for GrapesJS landing pages, email templates,
  MkDocs export, and documentation editor Insert dropdown
- Shared HTML generators in admin/src/utils/videoCardHtml.ts
- MkDocs video-player.js hydrates .video-card-block elements:
  thumbnail fix via MEDIA_API_URL, click-to-play inline, Gallery link
- Media API CORS: auto-add MkDocs + docs subdomain origins
- env_config_hook.py: smart Docker hostname detection, ADMIN_PORT
  resolution, pass env vars to MkDocs container
- Gallery URL uses /gallery?expanded=ID format
- VideoPickerModal: fix double /api prefix and Docker hostname thumbs
- Seed: default-video-card PageBlock
- Remove V1 legacy code (influence/, map/)

Bunker Admin

.env.example

@@ -174,6 +174,7 @@ USER_NAME=coder
 
 # --- Homepage ---
 HOMEPAGE_PORT=3010
+HOMEPAGE_EMBED_PORT=8887
 HOMEPAGE_VAR_BASE_URL=http://localhost
 
 # --- Mini QR ---