charts/libredb-studio/README.md's link to docs/MFA.md breaks once mirrored into the operator copy

## What

charts/libredb-studio/README.md links to docs/MFA.md with a relative path that breaks once the file is mirrored into the operator's copy of the chart.

## Where

charts/libredb-studio/README.md:178:

```
[`docs/MFA.md`](../../docs/MFA.md).
```

This resolves correctly from charts/libredb-studio/README.md, since two levels up from there reaches the repo root. Per CONTRIBUTING.md, operator/helm-charts/libredb-studio/ is a byte for byte mirror of this chart, generated by `bun run chart:bump`. Once mirrored one directory deeper, the same relative path resolves to operator/docs/MFA.md, which does not exist.

## Expected

The link resolves correctly whichever copy of the README it is read from.

## How to fix

1. Do not hand edit operator/helm-charts/libredb-studio/README.md directly. CONTRIBUTING.md says the mirrored copy must never be edited by hand.
2. In charts/libredb-studio/README.md, change the docs/MFA.md link to an absolute GitHub URL, for example `https://github.com/libredb/libredb-studio/blob/main/docs/MFA.md`.
3. Run `bun run chart:bump` to regenerate the operator mirror, and commit both files together.

## How to check

`bun run chart:check` passes, and the MFA.md link resolves correctly both from charts/libredb-studio/README.md and from operator/helm-charts/libredb-studio/README.md.

Start at charts/libredb-studio/README.md:178 and read CONTRIBUTING.md for the chart mirror workflow. Update the source README link, run `bun run chart:bump` to regenerate operator/helm-charts/libredb-studio/README.md, then run `bun run chart:check`. Done means both README copies contain a working MFA.md link and the check passes.

Written by the indexing model from the issue text.