df shouldn't use -h as it depends on locale

Check for other issues

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Issue description

df -h returns different number formats depending on user locale, which in certain european countries can be using , instead of a . as the separator, making the numbers wrong. Omitting -h shows the byte count as a single number that's easier to parse.

Steps to reproduce

1. Set system locale to one using commas for decimal separators (most european)
2. Open Spacedrive and check volume size

Platform and versions

• OS: Linux NixOS

• Spacedrive: 6dfeccf2113039e35f2ce735f945e70dc3e4ea45

  bun 1.3.13 cargo 1.97.0 (c980f4866 2026-06-30) rustc 1.97.1 (8bab26f4f 2026-07-14)

Stack trace

Additional context

https://github.com/spacedriveapp/spacedrive/blob/6dfeccf2113039e35f2ce735f945e70dc3e4ea45/core/src/volume/platform/linux.rs#L36

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