Qt: fix receive request model handling

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PR intention

Fix critical receive-request dialog crashes and filtered recent-request history mis-handling in the Qt wallet.

Code changes brief

• Pass the full WalletModel to ReceiveRequestDialog and derive the options model from it so address-type validation does not dereference an uninitialized pointer.
• Map recent-request selections from the filter proxy to source rows before copying/deleting.
• Remove selected source rows in descending order so filtered multi-delete cannot erase the wrong persisted requests.