Mobile build size analysis crashes for Android AAB uploads

### Self-Hosted Version

26.8.0

### CPU Architecture

aarch64

### Docker Version

Docker version 29.8.0, build 88096ef

### Docker Compose Version

Docker Compose version v5.5.1

### Machine Specification

- [x] My system meets the minimum system requirements of Sentry

### Installation Type

New feature on upgraded instance
(EDIT: This feature rolled out a few releases ago, but we are only trying it out for the first time now so it may not be related specifically to 26.8.0)

### Steps to Reproduce

Build a .NET MAUI app and produce an iOS `.ipa` and an Android `.aab`.
Sample repo has been provided [here](https://github.com/beeradmoore/MauiSentryTest), pre-compiled `.aab` can be provided on request.

`build.sh` will build the iOS and Android apps.
`upload.sh` will upload the relevant `.ipa` and `.aab`. This assumes your environment is setup with a correct `.sentryclirc` which lists org and project.

### Expected Result

Able to see the size breakdown of [size analysis](https://docs.sentry.io/product/size-analysis/) by going to Project -> Releases -> Mobile Builds

### Actual Result

iOS shows as expected.

Android throws an exception when trying to process the `.aab`.

Additionally when looking at the `Mobile Builds` tab it does not show

Uploading the same files to a SaaS instance works as expected for both size analysis and listing size in the table.

Here is a copy of the exception thrown on screen.

[2026-09-15 - sentry-size-monitoring-issue.txt](https://github.com/user-attachments/files/32266330/2026-09-15.-.sentry-size-monitoring-issue.txt)

### Event ID

_No response_

Use the linked MauiSentryTest repository, starting with build.sh and upload.sh to reproduce the iOS and Android uploads in the self-hosted setup. Read the attached sentry-size-monitoring-issue.txt exception and compare the self-hosted processing path with the SaaS behavior. Done means the Android AAB is processed without an exception and appears in Mobile Builds with its size breakdown.

Written by the indexing model from the issue text.