Updates to facilitate Trezor integration in mobile

[ovitrif]

While reviewing the watch-only hardware-wallet layer on this branch, a few things stood out that would be better owned by core than reimplemented per-platform.

Note: I diffed against the local bitkit-core checkout, which is at 0.1.40 and predates the watcher / wallet-scoped-activity surface this PR consumes from 0.3.2 — so these are against the consumed 0.3.2 binary, not the source. Flagging in case the source needs a bump too.

Subtasks

• 1. Core should own the wallet_id derivation
  The per-device id is improvised on the Swift side (HwWalletId.derive = "trezor:" + SHA256(sorted xpubs)) and the PR already flags it as interim pending agreement with Android. If iOS and Android derive it independently, the same physical device yields different ids and activity won't reconcile cross-platform. Suggest a core deriveWalletId(xpubs:) so both platforms are guaranteed identical by construction.
• 2. Have the watcher emit Activity instead of HistoryTransaction
HwWalletManager.onchainActivity() hand-reconstructs an Activity from HistoryTransaction — guessing direction from received > sent, netting the fee, and hardcoding feeRate: 1 / address: "". That's core's job, and the placeholder fee-rate will render wrong. Emitting Activity (or exposing a watchOnlyActivityFromHistory(walletId:txs:) mapper) removes a per-platform mapping that iOS and Android will otherwise drift on.
• 3. gapLimit: 20 should be a core default
  instead of being duplicated in HwWalletManager and the watcher params on each platform.
• 4. Core should own supported hardware-wallet metadata and capabilities
  Android currently carries supported-device display metadata in app code while Trezor is only one concrete implementation of the generic hardware-wallet layer. Expose the supported vendors/models/capabilities from core so Android and iOS can render supported devices generically instead of duplicating Trezor-specific supported-HW info per platform. Follow-up from feat: transfer to spending from hw wallet bitkit-android#1039.

Originally posted by @jvsena42 in synonymdev/bitkit-ios#605 (comment)

[ovitrif]

@coreyphillips I added subtask 4, it's not as critical as the others but also can't be delayed too much 🙏🏻

Should be an easy fix though, basically just modeling the type(s) of supported HWWs vendors, only Trezor for now:

See:
synonymdev/bitkit-android#1039 (comment) (resolved, screengrab above)