feat(backend): enhance social previews for single-file shares

Implements dynamic Open Graph (OG) metadata and image generation for
single-file shared boxes to improve social media previews.

Changes include:
- Added a new route `/d/{boxID}/f/{fileID}/og-image.jpg` for file-specific OG images.
- Updated `DownloadPage` to dynamically set the page title, description, and OG image properties when a box contains only one file.
- Restricted raw media inline serving for social bots to images and videos.
- Added helper functions to format file share descriptions and determine appropriate social image URLs and types.
- Integrated basic font rendering to support dynamic OG image generation.

backend/templates/layouts/base.html

@@ -11,16 +11,30 @@
   <meta name="generator" content="Warp Box {{.AppVersion}}">
 
   <meta property="og:site_name" content="{{.AppName}}">
-  <meta property="og:type" content="website">
+  <meta property="og:type" content="{{if .OGType}}{{.OGType}}{{else}}website{{end}}">
   <meta property="og:title" content="{{if .Title}}{{.Title}}{{else}}{{.AppName}}{{end}}">
   <meta property="og:description" content="{{.Description}}">
   <meta property="og:url" content="{{if .CanonicalURL}}{{.CanonicalURL}}{{else}}{{.BaseURL}}{{end}}">
   {{if .ImageURL}}
   <meta property="og:image" content="{{.ImageURL}}">
+  <meta property="og:image:secure_url" content="{{.ImageURL}}">
+  {{if .ImageType}}<meta property="og:image:type" content="{{.ImageType}}">{{end}}
   <meta property="og:image:width" content="1200">
   <meta property="og:image:height" content="630">
   {{if .ImageAlt}}<meta property="og:image:alt" content="{{.ImageAlt}}">{{else}}<meta property="og:image:alt" content="{{.AppName}} preview">{{end}}
   {{end}}
+  {{if .MediaURL}}
+  {{if eq .OGType "video.other"}}
+  <meta property="og:video" content="{{.MediaURL}}">
+  <meta property="og:video:secure_url" content="{{.MediaURL}}">
+  {{if .MediaType}}<meta property="og:video:type" content="{{.MediaType}}">{{end}}
+  {{end}}
+  {{if eq .OGType "music.song"}}
+  <meta property="og:audio" content="{{.MediaURL}}">
+  <meta property="og:audio:secure_url" content="{{.MediaURL}}">
+  {{if .MediaType}}<meta property="og:audio:type" content="{{.MediaType}}">{{end}}
+  {{end}}
+  {{end}}
 
   <meta name="twitter:card" content="summary_large_image">
   <meta name="twitter:title" content="{{if .Title}}{{.Title}}{{else}}{{.AppName}}{{end}}">