add support for video previews (#197)

* add support for video previews

* fix two cases where video previews did not show

src/utils/media.ts

@@ -0,0 +1,53 @@
+/**
+ * Media file utility functions
+ */
+
+const VIDEO_EXTENSIONS = [
+  '.mp4',
+  '.webm',
+  '.mov',
+  '.avi',
+  '.mkv',
+  '.flv',
+  '.wmv',
+  '.m4v',
+  '.ogv',
+]
+
+const VIDEO_HOST_PATTERNS = [
+  '/video', // Civitai video URLs often end with /video
+  'type=video', // URLs with video type parameter
+  'format=video', // URLs with video format parameter
+  'video.civitai.com', // Civitai video domain
+]
+
+/**
+ * Detect if a URL points to a video based on extension or URL patterns
+ * @param url - The URL to check
+ * @param localContentType - Optional MIME type for local files
+ */
+export const isVideoUrl = (url: string, localContentType?: string): boolean => {
+  if (!url) return false
+
+  // For local files with known MIME type
+  if (localContentType && localContentType.startsWith('video/')) {
+    return true
+  }
+
+  const urlLower = url.toLowerCase()
+
+  // First check if URL ends with a video extension
+  for (const ext of VIDEO_EXTENSIONS) {
+    if (urlLower.endsWith(ext)) {
+      return true
+    }
+  }
+
+  // Check if URL contains a video extension anywhere (for complex URLs like Civitai)
+  if (VIDEO_EXTENSIONS.some((ext) => urlLower.includes(ext))) {
+    return true
+  }
+
+  // Check for specific video hosting patterns
+  return VIDEO_HOST_PATTERNS.some((pattern) => urlLower.includes(pattern))
+}