syncFromBlockchain
Sync shielded state from blockchain.
Queries all zswap events, replays into ZswapLocalState, persists. For now: full replay from genesis (incremental sync in Phase 2).
Return
true if sync succeeded and coins found
Parameters
address
Wallet address (for DataStore key)
zswapSeed
32-byte zswap seed (derived at m/44'/2400'/0'/3/0)