Panic during Oidc login

I was trying to login using Oidc and when I was back to the application (so after login and continue on the MAS page) I got a crash.

Rageshake: https://github.com/element-hq/element-x-android-rageshakes/issues/5680

The logcat file contains more details about the problem.

Extract:

```
2025-05-07T09:18:53.701599Z ERROR elementx: Failed to login with OIDC
org.matrix.rustcomponents.sdk.OidcException$Generic: An error occurred: authorization code grant failed: failed to request token: Server returned error response: server_error: The authorization server encountered an unexpected condition that prevented it from fulfilling the request.
at org.matrix.rustcomponents.sdk.FfiConverterTypeOidcError.read(matrix_sdk_ffi.kt:34537)
at org.matrix.rustcomponents.sdk.FfiConverterTypeOidcError.read(matrix_sdk_ffi.kt:34529)
at org.matrix.rustcomponents.sdk.FfiConverter$DefaultImpls.liftFromRustBuffer(matrix_sdk_ffi.kt:237)
at org.matrix.rustcomponents.sdk.FfiConverterRustBuffer$DefaultImpls.liftFromRustBuffer(matrix_sdk_ffi.kt:249)
at org.matrix.rustcomponents.sdk.FfiConverterTypeOidcError.liftFromRustBuffer(matrix_sdk_ffi.kt:34529)
at org.matrix.rustcomponents.sdk.FfiConverterTypeOidcError.liftFromRustBuffer(matrix_sdk_ffi.kt:34529)
at org.matrix.rustcomponents.sdk.FfiConverterRustBuffer$DefaultImpls.lift(matrix_sdk_ffi.kt:250)
at org.matrix.rustcomponents.sdk.FfiConverterTypeOidcError.lift(matrix_sdk_ffi.kt:34529)
at org.matrix.rustcomponents.sdk.FfiConverterTypeOidcError.lift(matrix_sdk_ffi.kt:34529)
at org.matrix.rustcomponents.sdk.OidcException$ErrorHandler.lift(matrix_sdk_ffi.kt:34525)
at org.matrix.rustcomponents.sdk.OidcException$ErrorHandler.lift(matrix_sdk_ffi.kt:34524)
at org.matrix.rustcomponents.sdk.Matrix_sdk_ffiKt.uniffiCheckCallStatus(matrix_sdk_ffi.kt:313)
at org.matrix.rustcomponents.sdk.Matrix_sdk_ffiKt.access$uniffiCheckCallStatus(matrix_sdk_ffi.kt:1)
at org.matrix.rustcomponents.sdk.Matrix_sdk_ffiKt.uniffiRustCallAsync(matrix_sdk_ffi.kt:45053)
at org.matrix.rustcomponents.sdk.Matrix_sdk_ffiKt$uniffiRustCallAsync$1.invokeSuspend(Unknown Source:19)
at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:100)
at kotlinx.coroutines.internal.LimitedDispatcher$Worker.run(LimitedDispatcher.kt:124)
at kotlinx.coroutines.scheduling.TaskImpl.run(Tasks.kt:89)
at kotlinx.coroutines.scheduling.CoroutineScheduler.runSafely(CoroutineScheduler.kt:586)
at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.executeTask(CoroutineScheduler.kt:820)
at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.runWorker(CoroutineScheduler.kt:717)
at kotlinx.coroutines.scheduling.CoroutineScheduler$Worker.run(CoroutineScheduler.kt:704)
| RustMatrixAuthenticationService.kt:250
2025-05-07T09:18:53.766901Z ERROR log: thread '' panicked at 'there is no reactor running, must be called from the context of a Tokio 1.x runtime': /home/runner/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/deadpool-runtime-0.1.4/src/lib.rs:101
```

Start with the OIDC login failure at RustMatrixAuthenticationService.kt:250 and compare it with the linked rageshake and logcat extract. Trace the authorization code grant failure and the reported Tokio reactor panic, then reproduce the login path and verify that this error no longer crashes the application.

Written by the indexing model from the issue text.