The YARP routes, the bucket path transform and the StreamTicket section only
existed in appsettings.Development.json, so a Production run had no routes at
all and every /media request fell through to a 404. Move them to
appsettings.json and leave only the environment-specific overrides (key path)
in the Development file; the container gets the filer address, the bucket and
the allowed CORS origins from environment variables.
- Move all .NET (6 projects, solution, Directory.*.props, nuget.config)
into backend/ so the monorepo root can host non-.NET projects later
- Remove throwaway test artifacts: player.html, pl.json
- Trim dead Flutter rules from .gitignore
Build from backend/Musify.slnx: 0 warnings, 0 errors.