add dynamic profile update, connection helper, file download metadata

- replace UserSetColor/UserSetPronouns with single UserUpdateProfile that dynamically builds one UPDATE query from UserProfileUpdateList
- add getConnectionWithResponseOnFail helper to deduplicate connection ID parsing and validation across handlers
- rename file.go to attachmentFile.go and update handler names
- GetDownloadUrlAndMetadata now fetches object metadata via StatObject and returns it alongside the presigned URL
- file download endpoint returns JSON with url and originalName
- add description field to user and DB schema
- remove unused ConnectionState variants (GroupFellow, GroupFriend)

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

main.go

@@ -31,14 +31,14 @@ func main() {
 	http.HandleFunc("/new/user", withCORS(httpRequest.HandleUserNew))
 	http.HandleFunc("/new/connection", withCORS(httpRequest.HandleUserNewConnection))
 	http.HandleFunc("/new/token", withCORS(httpRequest.HandleUserNewToken))
-	http.HandleFunc("/new/file", withCORS(httpRequest.HandleFileUpload))
+	http.HandleFunc("/new/file", withCORS(httpRequest.HandleAttachmentFileUpload))
 	http.HandleFunc("/mod/user/appearence", withCORS(httpRequest.HandleUserModifyAppearance))
-	http.HandleFunc("/mod/user/about", withCORS(httpRequest.HandleUserModifyAbout))
+	http.HandleFunc("/mod/user/about", withCORS(httpRequest.HandleUserModProfile))
 	http.HandleFunc("/mod/connection/accept", withCORS(httpRequest.HandleUserElevateConnection))
 
 	http.HandleFunc("/get/connections", withCORS(httpRequest.HandleUserGetConnections))
 	http.HandleFunc("/get/connection/messages", withCORS(httpRequest.HandleUserGetConnectionMessages))
-	http.HandleFunc("/get/file", withCORS(httpRequest.HandleFileDownload))
+	http.HandleFunc("/get/file", withCORS(httpRequest.HandleAttachmentFileDownload))
 
 	http.HandleFunc("/del/user", withCORS(httpRequest.HandleUserDelete))
 	http.HandleFunc("/del/connection", withCORS(httpRequest.HandleUserDeleteConnection))