Android app does not open .xlsm files in Nextcloud Office, while .xlsx files work

### ⚠️ Before posting ⚠️

- [x] This is a **bug**, not a question or an enhancement.
- [x] #17420
- [x] I've written a clear and descriptive title for this issue, not just "Bug" or "Crash".
- [x] I agree to follow Nextcloud's [Code of Conduct](https://nextcloud.com/contribute/code-of-conduct/).

### Steps to reproduce

1. Connect the official Nextcloud Android app to a Nextcloud AIO server with Nextcloud Office enabled.
2. Upload or select an Excel ".xlsm" file containing macros.
3. Tap the ".xlsm" file in the Nextcloud Android app.
4. Android displays the system "Open with" dialog instead of opening the file in Nextcloud Office.
5. Tap an ".xlsx" file in the same Nextcloud account.
6. The ".xlsx" file opens correctly in Nextcloud Office from within the Android app.
7. Create a share link for the same ".xlsm" file and open the link in a mobile browser.
8. The ".xlsm" file opens and can be edited correctly in Nextcloud Office in the browser.

The issue occurs with both the standard Nextcloud Office/Collabora integration and EuroOffice.

### Expected behaviour

Tapping an ".xlsm" file in the official Nextcloud Android app should open the document directly in Nextcloud Office, in the same way that ".xlsx" files do.

### Actual behaviour

When tapping an `.xlsm` file, Android shows the system "Open with" dialog instead of opening the document in Nextcloud Office.

The same `.xlsm` file opens and can be edited correctly in Nextcloud Office when opened through a share link in the mobile browser.

Regular `.xlsx` files open correctly in Nextcloud Office directly from the Android app.

The same behaviour occurs with both Nextcloud Office/Collabora and EuroOffice.

### Android version

Android 16

### Device brand and model

Xiaomi Redmi Pad 2 5G (2509BRP2DG)

### Stock or custom OS?

Stock

### Nextcloud android app version

34.1.0

### Nextcloud server version

Nextcloud AIO v13.4.0

### Using a reverse proxy?

Yes

### Android logs

_No response_

### Server error logs

```bash

```

### Additional information

_No response_

Start by reproducing the Android app behavior with an .xlsm file and compare it with .xlsx, using the stated Nextcloud Office and EuroOffice setups. Trace the app's file-opening and type-handling entry points for these extensions. Done means tapping .xlsm opens it directly in Nextcloud Office, matching .xlsx behavior, without the Android "Open with" dialog.

Written by the indexing model from the issue text.