fix: boltz 0.5.2 restore hardening — rescue skipped-swap reporting (6.12.6+206)

[i5hi]

Internal test build for the users failing to claim/refund restored swaps. Based off main (6.12.4+201) so the only delta vs what those users run is the restore fix chain.

What

• bull_sdk pin → 344a04e (bump-boltz-0.5.2-for-6.12.x): the app's current pin (bd4835c) plus ONLY boltz-dart 0.5.2 (develop 6f75525 — boltz-dart Recieve Page Address Label Save  #56/Unable to change Tx label #57/Addresses In Wallet Settings page should load addresses #58/Updated BackButton in appBar component #59/Recover wallet should support 24 words #60/Make wallet label mandatory on new wallets #61). Deliberately NOT bull_sdk main (a4dd62d, PR Bug when creating unsigned PSBTs #20): that tip also carries the ark.dart removal and lwk's u64→BigInt API change, both compile-breaking on app main and unrelated to this diagnostic build. Develop takes PR Bug when creating unsigned PSBTs #20's pin later together with its ark/lwk state.
• Restore call-site migration to the new Restored*Swaps { swaps, skipped } API: datasource wrapper return types, and the five rescueSwap lookups now search .swaps with a skipped-aware miss handler.
• Rescue failures name themselves: a swap the scan returned but couldn't rebuild throws swap <id> could not be rebuilt from restore: <reason> instead of the misleading "possibly beyond gap limit", and every skipped swap is logged (SWAP_RESTORE: swap <id> returned by scan but not rebuildable: ...) so user logs show it.
• Version bump 6.12.6+206 (versionCode above all distributed builds).

What this fixes for the affected users

• One submarine swap in the history no longer aborts the entire restore batch (Claim details required… — boltz-dart Recieve Page Address Label Save  #56), which previously blocked rescuing every other swap too.
• Submarine swaps restore even without a parseable BOLT11 invoice (refund needs neither preimage nor amount — boltz-dart Make wallet label mandatory on new wallets #61).
• Unrebuildable swaps are skipped, reported, and logged instead of silently vanishing or failing the batch.

Verification

• dart analyze lib test: 0 issues. Full test suite: 499/499.
• Underlying boltz-dart changes covered by 20 rust tests (5 new) + verified fund-path analysis (refund never reads preimage/amount; script hashlock comes from the swap tree).

Test protocol on the affected device

1. Settings → Bitcoin settings → Swap restore: list should populate (previously errored).
2. Rescue the stuck swap: refund should broadcast, or the UI/logs name the concrete rebuild failure.
3. Export logs: SWAP_RESTORE: lines show restored/skipped ids for diagnosis.

Note: develop owes main a merge-back of this after the release (along with the existing 6.12.x debt).