feat(ecash): adopt the reference NUT-02 resolver + real/test network switch

Executes steps 1-3 of docs/cashu-cdk-migration-plan.md, plus the test-coin
switch needed to exercise these routes without spending real sats.

Protocol layer: depend on `cashu` 0.17.5 (MIT, the crate CDK is built on,
default-features off, `wallet` only). Keyset ids now go through upstream's
`Id::from_short_keyset_id` / `ShortKeysetId` instead of the prefix match
hand-rolled in 2277fc46 — same repair, but implemented by the reference
code that defines the rule, so the next spec turn is a version bump rather
than another incident. `MintClient` feeds it the mint's `/v1/keysets` in
upstream's own `KeySetInfo` shape, parsing entries individually so one
keyset in an unmodelled unit can't block resolving the id we need.

Adding the crate required relaxing `bip39 = "=2.1.0"` to `"2.1"` (resolves
2.2.2): the exact pin held `unicode-normalization` at 0.1.22 and no
resolution existed otherwise. The pin carried no recorded rationale; seed
tests cover the bump.

Network switch: `wallet.ecash-network` / `wallet.ecash-set-network`, with a
Test mode toggle in Wallet Settings → Cashu. Cashu has no testnet, so this
points the wallet at the public `testnut` mint — but crucially each network
gets its OWN wallet and accepted-mints file, because test and real proofs
in one purse would be spendable interchangeably and the balance would be a
lie. Mainnet keeps the original filenames, so existing funds files are
untouched and switching is reversible: tests assert a real balance survives
a round trip through test mode.

Headless coverage: scripts/test-ecash-routes.sh drives every ecash RPC over
the real HTTP path (network get/set, balance, history, mint quote + claim,
send, receive, double-redeem refusal, garbage input, melt quote), restores
the node's original network on exit, and exits non-zero with the failure
count.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

core/archipelago/src/api/rpc/dispatcher.rs

@@ -266,6 +266,8 @@ impl RpcHandler {
             "wallet.ecash-send" => self.handle_wallet_ecash_send(params).await,
             "wallet.ecash-receive" => self.handle_wallet_ecash_receive(params).await,
             "wallet.ecash-history" => self.handle_wallet_ecash_history().await,
+            "wallet.ecash-network" => self.handle_wallet_ecash_network().await,
+            "wallet.ecash-set-network" => self.handle_wallet_ecash_set_network(params).await,
             "wallet.networking-profits" => self.handle_wallet_networking_profits().await,
             // Fedimint ecash (via fedimint-clientd sidecar)
             "wallet.fedimint-list" => self.handle_wallet_fedimint_list().await,