[Bug] Buzz Desktop — lossy migration and failure to add relay

**Describe the bug**

After running the in-app update to 0.4.26, app data is apparently lost and log-in flow begins fresh. Adding a self-hosted relay fails immediately with the error **"The string did not match the expected pattern."** It fails for any relay URL, including a known-good public nostr relay, and no connection ever reaches the relay — so it's failing client-side before connecting. A quick search revealed that some settings like my main identity and 4 other agent keys correctly into the Keychain were still available in ios Keychain Access, but the app's web-side settings were wiped and a user-created agent was dropped.

**To Reproduce:**
1. Run the in-app update to 0.4.26.
2. Open the app and experience the fresh log-in flow.
3. Attempt to add a self-hosted relay.
4. Enter any relay URL (e.g. `wss://relay.damus.io`).
5. See error: "The string did not match the expected pattern."

**Expected behavior:**

1. Data is migrated correctly, including web-side settings and user-created agents.
2. In event of failed migration, adding a relay succeeds and connects to the relay.

**Supporting Material**

- Confirmed the relay itself is healthy — a raw WebSocket handshake from the same Mac returns `HTTP/1.1 101 Switching Protocols`.
- Confirmed no connection is attempted: tailing the relay logs (`journalctl -u buzz-relay -f`) shows nothing when "Add" is clicked.
- Same error occurs with `wss://relay.damus.io`, so it is not specific to my relay or its URL.

**Environment (please complete the following information):**
- OS: macOS 26.5.2 (build 25F84), Apple M1 Pro, 16 GB RAM (MacBookPro18,3)
- Version: 0.4.26 (installed via in-app update)