Crashlytics Gradle plugin does not register uploadCrashlyticsMappingFile when R8 is enabled via AGP 9.3 optimization.enable

### [READ] Step 1: Are you in the right place?

Issues filed here should be about bugs in **the code in this repository**. If you have a general
question, need help debugging, or fall into some other category use one of these other channels:

- For general technical questions, post a question on [StackOverflow](http://stackoverflow.com/)
with the firebase tag.
- For general Firebase discussion, use the
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- For help troubleshooting your application that does not fall under one of the above categories,
reach out to the personalized [Firebase support channel](https://firebase.google.com/support/).

### [REQUIRED] Step 2: Describe your environment

- Android Studio version: **Android Studio Quail 4 | 2026.1.4 RC 1**
- Firebase Component: **Crashlytics Gradle plugin**
- Component version: **3.0.7** (`com.google.firebase:firebase-crashlytics-gradle:3.0.7`)
- Android Gradle Plugin: **9.3.1**
- Gradle: **9.7.0**
- Google Services plugin: **4.5.0**
- Firebase Android BOM: **34.17.0**

### [REQUIRED] Step 3: Describe the problem

On AGP 9.3+, R8 is enabled with the new `optimization.enable = true` DSL ([docs](https://developer.android.com/topic/performance/app-optimization/enable-app-optimization)).
R8 runs and produces `mapping.txt`, but Crashlytics Gradle plugin
**3.0.7 does not register** `uploadCrashlyticsMappingFile` which should upload this mapping to firebase, this leads to unobfuscated crash reports in the Firebase console.