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/Models/Post/Post.cs

@@ -46,6 +46,8 @@ namespace PrivaPub.Models.Post
 		public PostPlace Place { get; set; }
 		[BsonIgnoreIfNull]
 		public PostPoll Poll { get; set; }
+		[BsonIgnoreIfNull]
+		public List<PostFlair> Flairs { get; set; }
 		public List<float> Location { get; set; } = new();
 		public float RangeKm { get; set; } = 5.0f;
 		[BsonIgnoreIfNull]

PrivaPub/Models/Post/PostDetails.cs

@@ -38,6 +38,19 @@
 		public List<string> Manual { get; set; } = new();
 	}
 
+	// a community's label on a post (Lemmy 1.0's CommunityPostTag, PieFed's lemmy:CommunityTag): one of the community's own
+	public class PostFlair
+	{
+		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; }//Lemmy's colour slot, color01 to color10
+		public string TextColor { get; set; }//PieFed's, as #rrggbb
+		public string BackgroundColor { get; set; }
+		public bool BlurImages { get; set; }
+	}
+
 	public class PostSource
 	{
 		public string Content { get; set; }

PrivaPub/Models/User/Avatar.cs

@@ -77,6 +77,7 @@ namespace PrivaPub.Models.User
 		public string InboxURL { get; set; }
 		public string OutboxURL { get; set; }
 		public string FeaturedURL { get; set; }//featured: the posts it pins
+		public List<PrivaPub.Models.Post.PostFlair> Flairs { get; set; } = new();//a community's labels for its posts
 		public string ModeratorsURL { get; set; }//a community's attributedTo (Lemmy, PieFed, Mbin): the collection of its moderators
 		public List<AssertionKey> AssertionKeys { get; set; } = new();//its Ed25519 keys (FEP-521a), which prove what it sends (FEP-8b32)
 		public string WallURL { get; set; }//sm:wall (FEP-400e): where others write to it, Smithereen's walls