feat: add trezor onchain event watcher

[coreyphillips]

Adds an Event Watcher section to the (dev-only) Trezor screen that consumes the new bitkit-core on-chain xpub watcher. Enter or populate an extended key, start/stop a live watcher, and observe streaming balance, transactions, connection status, and an event log.

Depends on bitkit-core 0.1.65

Description

• New WatcherSection composable: extended-key + gap-limit inputs, populate-from-xpub, start/stop controls, and a live view of balance, transactions, connection status, and an event log.
• TrezorViewModel:
  • Collects WatcherEvents from the repo and maps them into a new TrezorWatcherState (balance, transactions, tx count, block height, account type, connection status, event log).
  • Generates a per-session watcherId, validates the xpub/gap-limit inputs, and surfaces errors via toasts.
  • Stops the active watcher in onCleared() so no watcher thread is leaked.
• TrezorRepo: exposes a buffered watcherEvents SharedFlow bridged from a core EventListener, plus startWatcher / stopWatcher / stopAllWatchers returning Result<Unit>.
• TrezorService: thin wrappers over onchainStartWatcher / onchainStopWatcher / onchainStopAllWatchers.
• Bumped bitkit-core to 0.1.65 in libs.versions.toml.

QA Notes

• Build resolves bitkit-core 0.1.65.
• Dev Settings → Trezor → Event Watcher:
  • Populate from xpub (or paste an extended key), set a gap limit, and start the watcher; confirm status goes STARTING → CONNECTED and the initial balance/transactions populate.
  • Send a tx to the watched xpub and confirm the balance/tx list and event log update live.
  • Drop the network and confirm DISCONNECTED → CONNECTED transitions with a "Reconnected" log entry.
  • Stop the watcher and confirm state clears; leave/return to the screen and confirm no leaked watcher (stops on onCleared).
  • Invalid input (blank key, non-numeric gap limit) shows an error toast and does not start a watcher.
• Tests run: ./gradlew compileDevDebugKotlin, ./gradlew testDevDebugUnitTest --tests TrezorViewModelTest --tests TrezorRepoTest, ./gradlew detekt — all pass.

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