[@miden-sdk/miden-sdk] Upgrading 0.15.9 -> 0.16.0-rc.x on an existing store fails to deserialize and the client never starts

### Packages versions

@miden-sdk/miden-sdk: 0.15.9 -> 0.16.0-rc.7

### Bug description

Upgrading the client on an origin that already has a store leaves the app unable to start. `MidenDatabase.open()` throws before any network call:

```
Failed to create client: storage error: failed to deserialize data from the store: invalid value: Invalid public key
```

Nothing recovers from this. The user has to clear site data by hand, and there is no message telling them that is what is needed.

### Steps to reproduce

1. On a clean origin, run 0.15.9 and let it create an account, so the store has rows.
2. Load 0.16.0-rc.7 on the same origin.
3. `createTestnet()` fails with the error above.

With the same origin cleared first, rc.7 gets past this and fails at the RPC instead, which is the version mismatch you would expect against the current testnet:

```
accept header validation failed: server rejected request (client version: 0.16.0-rc.4, genesis commitment: none)
```

So the storage error is specific to having 0.15.9 rows present, not to rc.7 being unable to reach the network.

### Why the downgrade fix does not cover it

#355 catches `VersionError` around `dexie.open()` and wipes. That path is not reached here. rc.7 declares Dexie versions up to 5 while 0.15.9 stops at 2, so opening with the newer client is an upgrade, Dexie runs its own migration and nothing throws `VersionError`. What fails afterwards is reading 0.15.9 era rows with the newer deserializer.

### Notes

This is the direction most people will take when testnet moves to 0.16, so it seems worth handling as well as the downgrade. Widening the catch around `open()` to any store error and wiping would cover both, at the cost of dropping accounts and notes, which is already what the downgrade path does.

I hit this while building an app against 0.15.9, and again on our own deployment after testing rc.7 on the same origin, which bricked the 0.15.9 app until site data was cleared.

Look at the MidenDatabase.open() method and the surrounding error handling. The issue is that after a Dexie migration from version 2 to 5, deserialization of old rows (specifically public keys) fails. Examine the serialization/deserialization logic for account data. The fix likely involves catching a broader storage error during open and triggering a store wipe, similar to the downgrade handling in issue #355. Test by creating a store with version 0.15.9, then attempting to open it with 0.16.0-rc.7.

Written by the indexing model from the issue text.