EX: Inform users when fixing "key storage out of sync" fails

Nobody has claimed this yet.

For example:

1. On a different device:
1. reset cryptographic identity
2. set up recovery
3. using the developer tools, edit the `m.cross_signing.user_signing` account data item to remove the content of the `encrypted` object, thus: `{"encrypted": {} }`
2. Back on the device under test, enter the newly-created recovery key to re-verify
3. Observe "Your key storage is out of sync" toast; click "Continue"
4. Enter recovery key, click "Continue"
5. Back to step 3

In the logs, there is this line:

```
18:14:54.036 I matrix_sdk_crypto::store: Successfully imported the private cross-signing keys status=CrossSigningStatus { has_master: true, has_self_signing: true, has_user_signing: false } | crates/matrix-sdk-crypto/src/store/mod.rs:1321 | spans: recover > import_secrets{self=SecretStore { key: SecretStorageKey { storage_key_info: SecretStorageKeyEventContent { key_id: "JsOhg6wGuD18Qjv235PUioHOXojWNbi7", name: None, algorithm: V1AesHmacSha2(SecretStorageV1AesHmacSha2Properties { iv: Some("kR2sRxtvSEIX4xZWujQkrg"), mac: Some("ESubXhxa3xvA4oUMBfIiiS47U6TO9jdXXF3P4Rry0AI") }), passphrase: None }, .. }, .. } user_id=@af:xps9320.sw1v.org device_id=ZZTJDJERZH}
```

Obviously, the user-signing key is not being imported. The problem is that the process is failing silently.

Start with crates/matrix-sdk-crypto/src/store/mod.rs around line 1321 and trace the recover and import_secrets flow described in the logs. Reproduce the missing user-signing key scenario using the numbered steps, then inspect how an incomplete import is reported. Done means the failed key-storage repair produces a user-visible error instead of silently returning to the recovery flow.

Written by the indexing model from the issue text.