Route existing backups to recovery key entry

[pi0n00r]

Content

• When a server backup exists while local recovery is DISABLED, show and route to the existing enter-recovery-key flow instead of offering to set up new recovery.
• Map RustRecoveryException.Import through the application recovery-exception boundary instead of treating the import failure as a successful recovery.
• Add focused state, view-routing, and exception-mapping tests.

Motivation and context

Users with an existing server backup can reach a locally disabled recovery state. Offering setup-new recovery in that state sends them down the wrong path; the existing key-entry flow is the appropriate route.

Separately, an SDK room-key import failure must remain a failure so the UI can report it rather than proceeding as though recovery succeeded.

Related symptom report: #7283. This change may improve routing and import-error reporting for overlapping “key storage out of sync” cases, but it does not claim to fix that issue's reported incorrect-key cause or every historical Megolm restore failure.

Screenshots / GIFs

Not provided. The change reuses the existing recovery-key confirmation content and flow.

Tests

Focused tests were added for the new routing decision, its click target, and import-exception mapping.

Local tests were not run because the required Android toolchain was unavailable. GitHub-hosted PR CI is requested as the test substrate.

Tested devices

• Physical
• Emulator
• OS version(s): Not tested locally

Checklist

• I am aware of the etiquette.
• This PR was made with the help of AI:
  • Yes. In this case, please request a review by Copilot.
  • No.
• Changes have been tested on an Android device or Android emulator with API 24
• UI change has been tested on both light and dark themes
• Accessibility has been taken into account. See https://github.com/element-hq/element-x-android/blob/develop/CONTRIBUTING.md#accessibility
• Pull request is based on the develop branch
• Pull request title will be used in the release note, it clearly defines what will change for the user
• Pull request includes screenshots or videos if containing UI changes
• You've made a self review of your PR

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[github-actions]

Thank you for your contribution! Here are a few things to check in the PR to ensure it's reviewed as quickly as possible:

• If your pull request adds a feature or modifies the UI, this should have an equivalent pull request in the Element X iOS repo unless it only affects an Android-only behaviour or is behind a disabled feature flag, since we need parity in both clients to consider a feature done. It will also need to be approved by our product and design teams before being merged, so it's usually a good idea to discuss the changes in a Github issue first and then start working on them once the approach has been validated.
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[pi0n00r]

Thank you for considering this contribution. We will not sign the Element CLA because its commercial-relicensing terms fall outside our contribution policy. We are therefore withdrawing the contribution while preserving the patch in our fork. Element is welcome to implement the remedy independently.