Fix unknown sender names in Bluesky chats, reduce false notifications, and reorder Chats buffer

Resolve sender DIDs to display names by building member maps from conversation
data. Fix compose functions to prefer snake_case attributes (ATProto SDK convention).
Ensure stable key comparison in dedup logic by converting ATProto objects to strings.
Move Chats buffer to appear after Mentions and before Notifications.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/controller/buffers/blueski/base.py

@@ -1046,13 +1046,13 @@ class BaseBuffer(base.Buffer):
                 author = it.get("author")
                 if isinstance(author, dict):
                     return author.get("did") or author.get("handle")
-                # Chat message fallback
+                # Chat message fallback — use str() to ensure stable hash/comparison
                 sent_at = it.get("sentAt") or it.get("sent_at") or it.get("createdAt") or it.get("created_at")
                 sender = it.get("sender") or (nested.get("sender") if isinstance(nested, dict) else {}) or {}
                 sender_did = sender.get("did") if isinstance(sender, dict) else None
                 text = it.get("text") or (nested.get("text") if isinstance(nested, dict) else None)
                 if sent_at or sender_did or text:
-                    return (sent_at, sender_did, text)
+                    return (str(sent_at) if sent_at else None, str(sender_did) if sender_did else None, str(text) if text else None)
                 return None
             post = getattr(it, "post", None)
             if post is not None:
@@ -1075,7 +1075,7 @@ class BaseBuffer(base.Buffer):
             sender_did = getattr(sender, "did", None) if sender is not None else None
             text = getattr(it, "text", None) or (getattr(nested, "text", None) if nested is not None else None)
             if sent_at or sender_did or text:
-                return (sent_at, sender_did, text)
+                return (str(sent_at) if sent_at else None, str(sender_did) if sender_did else None, str(text) if text else None)
             return None
 
         for item in self.session.db[self.name]: