ios: add native Wavelength wallet

[bhandras]

Summary

• turn the iOS sample into a native SwiftUI wallet with balance, searchable
  activity, activity inspection, and Lightning/on-chain send and receive
• use Wavelength's Esplora-backed lightweight wallet rather than bundling LND
• add camera payment-request scanning and reusable QR codes for pending receive
  requests
• isolate signet, testnet3, mainnet, and debug regtest wallet state, with an
  explicit mainnet warning and network selection available before unlock
• add one-command Simulator build/test/run targets and opt-in live regtest tests

Activity and payment behavior

• incomplete Lightning invoices remain requests/pending; "received" is only
  shown after settlement
• on-chain deposit rows use Esplora-observed amounts rather than receive hints
• on-chain addresses and transaction IDs link to a network-appropriate explorer
• send confirmation presents the Wavelength quote before the user commits
• the app refreshes its snapshot every five seconds in addition to consuming
  the activity stream

Mobile transport recovery

• publish Activity and balance refresh results independently so one stalled
  source cannot suppress a successful update from the other
• request a 20-second native deadline for invoice creation
• treat the binding's stable uncertain-outcome error as a reconcile-before-retry
  signal for both deadline and lifecycle cancellation
• recover an invoice from the authoritative Activity view instead of blindly
  creating a second invoice after an uncertain result
• show a clear long-running state after five seconds rather than an unexplained
  spinner
• after a real iOS background/foreground transition, restart and unlock the
  same embedded wallet to re-dial external transports on the current path
• defer lifecycle teardown while state-creating operations are in flight, so
  transport recovery cannot cancel a payment or receive at an ambiguous point

Wavelength dependency

wavelength#1131 is
merged as da8903b633d0a45122eb2f5cbc72aeb307c52c98. Its source tree contains:

• bounded repeatable mobile reads;
• bounded Receive with a stable uncertain-outcome error contract;
• bounded optional credit enrichment; and
• btcwallet v0.18.1-0.20260826052527-33c252f3b4d6, which releases the wallet
  database transaction before remote recovery filtering.

This PR was built and tested against an xcframework generated from that exact
merged source tree. The reviewed PR head and merge commit have the same Git tree.

No Wavelength release tag currently contains the merge. The latest stable asset
is still v0.1.1. Until the next release is published, reproduce the validated
build by checking out da8903b633d0a45122eb2f5cbc72aeb307c52c98 in Wavelength
and running:

WAVELENGTH_DIR=/path/to/wavelength ./scripts/fetch-xcframework.sh

The framework remains an ignored build artifact. After the next Wavelength
release, scripts/fetch-xcframework.sh will download its published
Wavewalletdk.xcframework.tar.gz asset through the normal latest-release path.

Compatibility and rollout

Wavelength binding	Mobile wrapper	Result	Rollout
v0.1.1	this PR	TimeoutSeconds is ignored safely, but native reads and Receive remain unbounded	compatible fallback, not the complete fix
merged #1131	previous PR head	native bounds work; lifecycle-canceled Receive is not recognized as uncertain by Swift	short-lived source-validation combination only
merged #1131	this PR	every uncertain Receive outcome reconciles Activity before retry	intended final combination

The wrapper change only classifies returned errors. It does not alter persisted
wallet state, requests already in flight, or the Wavelength wire schema.

Safe rollout order:

1. publish a Wavelength release containing merge commit da8903b;
2. build the mobile app with that release's xcframework; and
3. validate signet or regtest receive recovery before distribution.

Validation

• built Wavewalletdk.xcframework from the exact merged Wavelength tree
• make test against that framework
  • 14 unit tests passed
  • 3 live regtest UI tests skipped as designed without endpoint opt-in
• new tests cover the stable uncertain-outcome prefix, the legacy deadline
  fallback, and an unrelated cancellation negative control
• companion Wavelength exact-head CI passed all 20 required checks, including
  mobile bindings, Postgres, race, lint, static checks, and cross-compilation
• manual Simulator validation of onboarding, network switching, balance,
  activity/details, QR scanning, and Lightning/on-chain send and receive
• manual signet validation on Simulator and a physical iPhone