feat(send): improve Lightning send failure recovery

[pwltr]

Summary

• Show the send failure screen for failed Lightning payments instead of surfacing raw/internal error text.
• Map LDKNode.PaymentFailureReason values to user-facing localized messages.
• Add dedicated routing failure copy for routeNotFound and retriesExhausted.
• Add Retry handling from the failure screen that resets payment routing caches, waits for required routing data, then returns the user to the correct send confirmation flow.
• Reset the send navigation stack on retry so Back does not return to the stale failure/confirmation path.
• Add localized strings for the new Lightning payment failure messages across supported locales.

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