No support for .well-known/matrix/server

The matrix spec permits hosting a file `.well-known/matrix/server` on the server's web root, delegating the server tasks to another hostname: https://spec.matrix.org/v1.9/server-server-api/#resolving-server-names

It appears that `matrix-commander` does not check this file:

```
% matrix-commander --login PASSWORD
Enter URL of your homeserver: [https://matrix.example.org] ohea.xyz
Enter your user ID: [@john:example.org] or [john] for @john:ohea.xyz : jrosenth
...
Correct? (Yes or Ctrl-C to abort) Yes
2024-01-20 17:14:53,701: ERROR: matrix-commander: E248: The program matrix-commander.py failed. Sorry.
2024-01-20 17:14:53,701: ERROR: matrix-commander: 404, message='Not Found', url=URL('https://ohea.xyz/_matrix/client/r0/login')
2024-01-20 17:14:53,701: INFO: matrix-commander: 2 errors and 0 warnings occurred.
```

(The file at https://ohea.xyz/.well-known/matrix/server should've been used here to determine the server's hostname is `matrix.ohea.xyz:443`).

Look at the login flow in matrix-commander.py, likely around URL handling. The spec describes server name resolution via .well-known/matrix/server. Start by finding where the homeserver URL is constructed and add a check for the well-known file. Test by simulating a server with delegation.

Vom Indexierungsmodell aus dem Issue-Text verfasst.