feat: narrow EdDSA MPC R/G share API and keep full state on AWM

[danielpeng1]

Tighten EdDSA MPC signing so the R round response and G round request match the updated AWM contract.

• AWM: R round returns EddsaUserToBitgoRShare only; G round decrypts encryptedUserToBitgoRShare + encryptedDataKey server-side (drop userToBitgoRShare from the API)
• Master-express: client types + G call forward commitment-round encrypted fields; R handler builds a minimal SDK SignShare (only rShares[BITGO] is used by the SDK)
• Breaking AWM ↔ master-express contract change; deploy both together

Tests:

• signMpcTransaction.test.ts: R response keys, G uses encrypted state, G fails without it
• Master eddsa / sendMany / signAndSendTxRequest mocks updated for new R/G bodies

Ticket: WCN-1930

[linear-code]

WCN-1930