feat: retry the swap restore for missed providers #1829

Follow-up from #1732 (Pubky Swaps routes, behind PUBKY_SWAPS_ROUTES on regtest debug builds).

The swap restore after a wallet restore asks each candidate provider once and never again:

• restoreSwaps reads its candidates from the contacts loaded when the backup restore completes. After a deferred Pubky session restore (retryDeferredSessionRestoration) that list can be empty, so nothing is found.
• bitkit-core reports providers whose swap list was not read in full as incompleteProviders and says to restore again for them; the app only logs them.
• bitkit-core asks at most 30 candidates for a route or a restore (MAX_CANDIDATES in feat: pubky swaps as paykit route bitkit-core#182). Configured providers come first, but contacts arrive alphabetically, so a provider sorting after the 30th contact is never tried.

Funds are not lost meanwhile: an unclaimed hold invoice expires back to Spending, and the provider refunds its own lock at the timeout.

Review threads:

• feat: pay contacts via pubky swaps #1732 (comment)
• feat: pay contacts via pubky swaps #1732 (comment)