feat(media): repurpose GIFs as video and serve converted mp4 when available

- Classify .gif as EAssetType.Video via MimeTypes (moved image/gif to the Video registry)
- Add MediaRepository.GetConvertedData, served by the existing media/{id} endpoint
  when a converted file exists on disk (with a fallback + warning log if missing)
- Expose the converted MIME type on AssetPreviewDto/AlbumAssetPreviewDto
  so the frontend can detect video assets from a single MimeType field

Butter/Dtos/Album/AlbumAssetPreviewDto.cs

@@ -27,6 +27,11 @@ public class AlbumAssetPreviewDto {
     /// </summary>
     public bool         HasPreview       { get; set; }
     /// <summary>
+    /// Gets or sets the MIME type of the asset's display media. For animated assets this is the
+    /// converted video MIME type (e.g. "video/mp4"); otherwise the original MIME type.
+    /// </summary>
+    public string       MimeType         { get; set; } = string.Empty;
+    /// <summary>
     /// Gets or sets the original filename of the asset.
     /// </summary>
     public string?      FileName         { get; set; }

Butter/MimeTypes.cs

@@ -26,7 +26,6 @@ public static class MimeTypes{
         new("image/bmp}", [".bmp"]),
         new("image/cgm", [".cgm"]),
         new("image/g3fax", [".g3"]),
-        new("image/gif", [".gif"]),
         new("image/heic", [".heif", ".heic"]),
         new("image/ief", [".ief"]),
         new("image/jpeg", [".jpe", ".jpeg", ".jpg", ".pjpg", ".jfif", ".jfif-tbnl", ".jif"]),
@@ -89,6 +88,8 @@ public static class MimeTypes{
     public static readonly MimeTypeMap[] Video = [
         new("video/3gpp", [".3gp"]),
         new("video/3gpp2", [".3g2"]),
+        // Animated GIFs are repurposed as video so they flow through the video rendering path.
+        new("image/gif", [".gif"]),
         new("video/h261", [".h261"]),
         new("video/h263", [".h263"]),
         new("video/h264", [".h264"]),

Lactose/Controllers/MediaController.cs

@@ -18,6 +18,7 @@ namespace Lactose.Controllers;
 /// <param name="mediaRepository">Media repository.</param>
 /// <param name="assetRepository">Asset repository.</param>
 /// <param name="signKeyOptions">JWT signing key configuration.</param>
+/// <param name="logger">Logger instance.</param>
 [ApiController]
 [Authorize]
 [AllowAnonymous]
@@ -26,7 +27,8 @@ public class MediaController(
     LactoseAuthService authService,
     IMediaRepository mediaRepository,
     IAssetRepository assetRepository,
-    IOptions<SignKeyConfiguration> signKeyOptions
+    IOptions<SignKeyConfiguration> signKeyOptions,
+    ILogger<MediaController> logger
 ) : ControllerBase {
 
     /// <summary>
@@ -43,15 +45,47 @@ public class MediaController(
         
         if (asset == null) return NotFound();
 
+        // Animated assets with a converted video on disk serve the converted file (and its MIME type),
+        // never the original animation. A stale ConvertedPath (file missing) falls back to the original.
+        bool hasConverted = HasConvertedFile(asset);
+
         if (CanAccessAssetDirectly(user, asset.DeletedAt)) {
+            if (hasConverted)
+                return PhysicalFile(asset.ConvertedPath, asset.ConvertedMimeType);
             return PhysicalFile(asset.OriginalPath, asset.MimeType);
         }
+
+        var converted = hasConverted
+            ? mediaRepository.GetConvertedData(id, user?.Id, user?.AccessLevel ?? EAccessLevel.User)
+            : null;
+        if (converted != null)
+            return PhysicalFile(converted.Path, converted.MimeType);
+
         var data = mediaRepository.GetOriginalData(id, user?.Id, user?.AccessLevel ?? EAccessLevel.User);
         if (data == null) return NotFound();
 
         return PhysicalFile(data.Path, data.MimeType);
     }
 
+    /// <summary>
+    /// Determines whether an asset has a converted video file available on disk.
+    /// Logs a warning when the converted path is set but the file is missing.
+    /// </summary>
+    /// <param name="asset">The asset to inspect.</param>
+    /// <returns><see langword="true"/> when the converted path and MIME type are set and the file exists.</returns>
+    private bool HasConvertedFile(Models.Asset asset) {
+        if (string.IsNullOrEmpty(asset.ConvertedPath) || string.IsNullOrEmpty(asset.ConvertedMimeType))
+            return false;
+
+        if (!System.IO.File.Exists(asset.ConvertedPath)) {
+            logger.LogWarning("Converted file for asset {AssetId} is missing on disk at {Path}; falling back to the original.",
+                asset.Id, asset.ConvertedPath);
+            return false;
+        }
+
+        return true;
+    }
+
     /// <summary>
     /// Gets the thumbnail image for an asset.
     /// </summary>

Lactose/Jobs/FileSystemCrawlJob.cs

@@ -296,8 +296,8 @@ public sealed class FileSystemCrawlJob : Job {
         var mimeImg = MimeTypes.Image.FirstOrDefault(mime => mime.Extensions.Contains(ext), new(Empty, []));
         var mimeVid = MimeTypes.Video.FirstOrDefault(mime => mime.Extensions.Contains(ext), new(Empty, []));
 
-        if (mimeImg.MimeType != Empty) type      = EAssetType.Image;
-        else if (mimeVid.MimeType != Empty) type = EAssetType.Video;
+        if (mimeVid.MimeType != Empty) type = EAssetType.Video;
+        else if (mimeImg.MimeType != Empty) type = EAssetType.Image;
         else return null;
 
         return new Asset {

Lactose/Mapper/AlbumMapper.cs

@@ -44,6 +44,7 @@ public static class AlbumMapper {
                 ResolutionHeight = asset.ResolutionHeight,
                 HasThumbnail     = !string.IsNullOrEmpty(asset.ThumbnailPath),
                 HasPreview       = !string.IsNullOrEmpty(asset.PreviewPath),
+                MimeType         = string.IsNullOrEmpty(asset.ConvertedMimeType) ? asset.MimeType : asset.ConvertedMimeType,
                 FileName         = accessLevel >= EAccessLevel.Curator ? asset.OriginalFilename : null,
                 Visibility       = accessLevel >= EAccessLevel.Maintainer ? asset.Visibility : null,
                 DeletedAt        = accessLevel >= EAccessLevel.Admin || asset.UploadedBy == viewerId ? asset.DeletedAt : null

Lactose/Mapper/AssetsMapper.cs

@@ -43,7 +43,7 @@ public static class AssetsMapper {
     /// <returns>A AssetPreviewDto object.</returns>
     public static AssetPreviewDto ToAssetPreviewDto(this Asset asset, EAccessLevel accessLevel, Guid? viewerId) => new AssetPreviewDto {
         Id               = asset.Id,
-        MimeType         = asset.MimeType,
+        MimeType         = string.IsNullOrEmpty(asset.ConvertedMimeType) ? asset.MimeType : asset.ConvertedMimeType,
         ResolutionWidth  = asset.ResolutionWidth,
         ResolutionHeight = asset.ResolutionHeight,
         HasThumbnail     = !string.IsNullOrEmpty(asset.ThumbnailPath),

Lactose/Repositories/AlbumRepository.cs

@@ -177,6 +177,7 @@ public class AlbumRepository(LactoseDbContext context) : IAlbumRepository {
                 ResolutionHeight = a.ResolutionHeight,
                 HasThumbnail     = a.ThumbnailPath != null && a.ThumbnailPath != "",
                 HasPreview       = a.PreviewPath != null && a.PreviewPath != "",
+                MimeType         = a.ConvertedMimeType != null && a.ConvertedMimeType != "" ? a.ConvertedMimeType : a.MimeType,
                 FileName         = accessLevel >= EAccessLevel.Curator ? a.OriginalFilename : null,
                 Visibility       = accessLevel >= EAccessLevel.Maintainer ? a.Visibility : null,
                 DeletedAt        = accessLevel >= EAccessLevel.Admin || a.UploadedBy == userId ? a.DeletedAt : null

Lactose/Repositories/AssetRepository.cs

@@ -317,7 +317,7 @@ public class AssetRepository(LactoseDbContext context, ILogger<AssetRepository>
             .Where(a => pageIds.Contains(a.Id))
             .Select(a => new AssetPreviewDto {
                 Id               = a.Id,
-                MimeType         = a.MimeType,
+                MimeType         = a.ConvertedMimeType != null && a.ConvertedMimeType != "" ? a.ConvertedMimeType : a.MimeType,
                 ResolutionWidth  = a.ResolutionWidth,
                 ResolutionHeight = a.ResolutionHeight,
                 HasThumbnail     = a.ThumbnailPath != null && a.ThumbnailPath != "",
@@ -459,7 +459,6 @@ public class AssetRepository(LactoseDbContext context, ILogger<AssetRepository>
         return new Butter.Dtos.Asset.AssetBrowseResultDto {
             Directories = dirs,
             Assets = assetDtos,
-            CurrentPath = currentPath,
             TotalAssetCount = totalAtLevel
         };
     }

Lactose/Repositories/IMediaRepository.cs

@@ -33,4 +33,13 @@ public interface IMediaRepository : IDisposable {
     /// <param name="accessLevel">The requesting user's access level.</param>
     /// <returns>A <see cref="MediaDto"/> containing the media data, or null if not found or unauthorized.</returns>
     public MediaDto? GetPreviewData(Guid id, Guid? userId, EAccessLevel accessLevel = EAccessLevel.User);
+
+    /// <summary>
+    /// Retrieves the converted media data (e.g. the mp4 for an animated GIF).
+    /// </summary>
+    /// <param name="id">The ID of the media.</param>
+    /// <param name="userId">The ID of the user requesting the media.</param>
+    /// <param name="accessLevel">The requesting user's access level.</param>
+    /// <returns>A <see cref="MediaDto"/> containing the converted media data, or null if the asset has no converted file or is not visible.</returns>
+    public MediaDto? GetConvertedData(Guid id, Guid? userId, EAccessLevel accessLevel = EAccessLevel.User);
 }

Lactose/Repositories/MediaRepository.cs

@@ -93,6 +93,20 @@ public class MediaRepository(LactoseDbContext context, IPersonRepository personR
         };
     }
 
+    /// <inheritdoc />
+    public MediaDto? GetConvertedData(Guid id, Guid? userId, EAccessLevel accessLevel = EAccessLevel.User) {
+        var media = GetVisibleAsset(id, userId, accessLevel);
+
+        if (media == null) return null;
+
+        if (string.IsNullOrEmpty(media.ConvertedPath) || string.IsNullOrEmpty(media.ConvertedMimeType)) return null;
+
+        return new MediaDto {
+            MimeType = media.ConvertedMimeType,
+            Path     = media.ConvertedPath
+        };
+    }
+
     /// <inheritdoc />
     public void Dispose() {
         context.Dispose();