Length converter uses an incorrect value for fathom-to-meter conversion

[fubai578]

Checklist

• I can reproduce the bug with the latest version given here.
• I made sure that there are no existing issues - open or closed - to which I could contribute my information.
• I made sure that there are no existing discussions - open or closed - to which I could contribute my information.
• I have read the FAQs inside the app (Menu -> About -> FAQs) and my problem isn't listed.
• I have taken the time to fill in all the required details. I understand that the bug report will be dismissed otherwise.
• This issue contains only one bug.
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Affected app version

### Affected Android/Custom ROM version

Android 14 (API 34)

### Affected device model

MuMu Android Emulator (900 x 1600)

### How did you install the app?

F-Droid / IzzyOnDroid

### Steps to reproduce the bug

1. Open the unit converter in Fossify Calculator and select **Length**.
2. Set the input unit to **Fathom** and the output unit to **Meter**.
3. Enter `1` as the input value and read the result.

### Expected behavior

The result should be `1.8288 m`, because one international fathom is exactly six feet, and six international feet equal 1.8288 meters.

### Actual behavior

The converter shows `1.852 m`. That value looks like the meter equivalent of a nautical mile rather than of a fathom.

### Screenshots/Screen recordings

<img width="900" height="1600" alt="Image" src="https://github.com/user-attachments/assets/4f5e9e72-fe38-4958-8420-aff73b7e1dc5" />

<img width="900" height="1600" alt="Image" src="https://github.com/user-attachments/assets/79971b9a-d1c4-4ba5-a943-3a82a2d6a055" />

### Additional information

- Package: `org.fossify.math`
- Tested version: 1.4.0 (version code 10)
- Environment: Android 14 (API 34), MuMu Android Emulator (900 x 1600)

The error is easy to spot for anyone who works with nautical units, and it propagates to every fathom value converted through this screen.