Skip network-backed mounts when enumerating UF2 drives

[Tudor (tudorjnu)]

When searching /media, /mnt, and similar paths for UF2-capable drives, os.listdir and os.path.isdir can hang indefinitely on network-backed filesystems (NFS, CIFS, SSHFS, autofs, network FUSE). Parse /proc/self/mountinfo to identify these mount points and skip them during enumeration. Local FUSE filesystems (exFAT, NTFS) are excluded from the skip list since they are not slow.

[Tudor (tudorjnu)]

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