Fix profile creation bugs

- platformWriteSeed (Android + iOS) invoked onSeedWritten twice on
  success, doubling wallet switch/navigation and navigating from the
  IO dispatcher; keep only the main-thread invocation.
- Gate profile event creation on the seed actually being written to
  disk: writeSeed now reports success/error, so a failed seed write no
  longer leaves orphaned unsigned events the notary can never sign.
- Stop rethrowing from createAccount's CoroutineExceptionHandler
  (crashed the app); failures now show the Error state and reset the
  pending flag instead of spinning forever. Add a re-entry guard
  against double taps.
- Reset WritingSeedState after a completed attempt so retries are not
  silently skipped, and record WrittenToDisk on success.
- Derive the nostr key with NodeParamsManager.chain instead of a
  hardcoded Chain.Mainnet.
- Build the SearchRelayListEvent from DefaultSearchRelayList instead
  of DM relays, and drop its empty privateTags array that caused a
  pointless NIP-44 encrypted empty list in content.
- Compare pubKey, privateTags and signedAt in UnsignedNostrEvent
  equals/hashCode so distinctUntilChanged cannot conflate rows.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

composeApp/src/iosMain/kotlin/press/mantra/compose/ui/view/model/NavigationViewModel.ios.kt

@@ -124,7 +124,6 @@ actual fun platformWriteSeed(
                 val newSeedMap = existingSeeds + (newWalletId to mnemonics)
                 val encrypted = EncryptedSeed.V2.encrypt(newSeedMap)
                 SeedManager.writeSeedToDisk(phoenixGlobal, encrypted, overwrite = true)
-                onSeedWritten.invoke(newWalletId)
                 if (isRestoringWallet) {
                     log.i("successfully restored wallet=$newWalletId")
                 } else {