P7: community flairs, from Lemmy and PieFed

- A post's flairs are read in both dialects: Lemmy 1.0's CommunityPostTag (id, slug, name, description, colour slot)
  and PieFed's lemmy:CommunityTag (display name, text and background colours, whether to blur images). Colours are
  kept only as a colour slot or a hex value.
- A community's own list comes from its `tag` and PieFed's older `lemmy:tagsForPosts`, and fills in a post that names
  only a flair's id and slug, as Lemmy's posts do. Edits and refreshes keep them current.
- Clients get them as `privapub.flairs`.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012CzABvBkbcFqoHdmi8b9WB

PrivaPub/Api/Mastodon/Entities/Entities.cs

@@ -79,6 +79,7 @@
 		public PrivaPubPlace Place { get; set; }//a remote post's own place (Pixelfed), shown only
 		public Account Wall { get; set; }//whose wall it was written on (FEP-400e), when not its author's
 		public PrivaPubVotes Votes { get; set; } = new();
+		public List<PrivaPubFlair> Flairs { get; set; } = new();
 	}
 
 	public class PrivaPubSource
@@ -163,6 +164,18 @@
 		public string Url { get; set; }
 	}
 
+	public class PrivaPubFlair
+	{
+		public string Id { get; set; }
+		public string Name { get; set; }
+		public string Slug { get; set; }
+		public string Description { get; set; }
+		public string Color { get; set; }
+		public string TextColor { get; set; }
+		public string BackgroundColor { get; set; }
+		public bool BlurImages { get; set; }
+	}
+
 	public class PrivaPubVotes
 	{
 		public int Up { get; set; }

PrivaPub/Api/Mastodon/Mappers/MastodonMapper.cs

@@ -543,7 +543,12 @@ namespace PrivaPub.Api.Mastodon.Mappers
 			{
 				Name = post.Place.Name, Latitude = post.Place.Latitude, Longitude = post.Place.Longitude, Country = post.Place.Country
 			},
-			Votes = new PrivaPubVotes { Up = post.FavouritesCount, Down = post.DownvotesCount }
+			Votes = new PrivaPubVotes { Up = post.FavouritesCount, Down = post.DownvotesCount },
+			Flairs = post.Flairs?.Select(f => new PrivaPubFlair
+			{
+				Id = f.Id, Name = f.Name, Slug = f.Slug, Description = f.Description, Color = f.Color, TextColor = f.TextColor,
+				BackgroundColor = f.BackgroundColor, BlurImages = f.BlurImages
+			}).ToList() ?? new()
 		};
 
 		PrivaPubVariant Variant(MediaVariant variant) => new()