[Self-Hosted] #0000 discriminator doesn't consider self-hosted instances

Summary

This issue is a reopening issue for #170 (got closed during bulk cleanup)

Username discriminator check when changing to #0000 only checks !isVisionary and doesn't consider self-hosted instances. https://github.com/fluxerapp/fluxer/blob/41ec2544cf3c048cf99c3e8d00bc84ad5308efdf/fluxer_app/src/features/user/components/modals/FluxerTagChangeModal.tsx#L318

Steps to reproduce

1. Setup self-hosted instance
2. On a non-visionary account, attempt to use #0000 discriminator.
3. Username modal shows error

Environment

Version: Latest (Self-Hosted) as of this issue sent. OS: Linux 7.0.11-1-cachyos Browser: Version 149.0.7827.53 (Official Build, ungoogled-chromium) Arch Linux (64-bit) Device: Desktop PC

Logs or screenshots

image