Merge develop into feature/50-upload-soundtrack

The API spec is now formatted like before (2-space indents, sorted keys):
develop's spec with the upload paths and types added, so the diff to
develop is only the upload API.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/generated/progress_response.gd

@@ -5,6 +5,7 @@ extends RefCounted
 ## The [code]ProgressResponse[/code] schema of the MusicServer API.
 
 var progress: String
+## How long the sync has been running, as minutes and seconds, e.g. "02:15"
 var time_spent: String
 
 

server/generated/sync_response.gd

@@ -10,6 +10,7 @@ var soundtracks_changed_content: Array[String]
 var soundtracks_changed_title: Dictionary[String, String]
 var soundtracks_re_added: Array[String]
 var soundtracks_removed: Array[String]
+## How long the sync took, as minutes and seconds, e.g. "02:15"
 var total_time: String