docs(kotlin-sdk): cite the Swift source in the signMessage KDoc

Kotlin-sdk porting guideline: when porting behavior from iOS, cite the
Swift source file in the KDoc, as the neighbouring methods do
(sendToAddresses -> SendViewModel.swift, tokens -> TokenActions.swift).
Names ManagedCoreWallet.signMessage(address:message:) and explains the
one signature divergence (Swift builds a per-call MnemonicResolver, so
it takes no signer parameter). Review follow-up from the original PR
(dashpay#4259).

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

Author: QuantumExplorer

packages/kotlin-sdk/sdk/src/main/kotlin/org/dashfoundation/dashsdk/wallet/ManagedPlatformWallet.kt

@@ -178,7 +178,11 @@ class ManagedPlatformWallet internal constructor(
      * signature as base64 — a **classic Dash signed message**, byte-for-byte
      * compatible with dashj's `ECKey.signMessage` and Dash Core's `signmessage`
      * RPC, and verifiable by `verifymessage`, `ECKey.verifyMessage`, and
-     * CrowdNode's server-side check.
+     * CrowdNode's server-side check. Android port of Swift's
+     * `ManagedCoreWallet.signMessage(address:message:)`
+     * (`ManagedCoreWallet.swift`), which takes no signer parameter because it
+     * builds a per-call `MnemonicResolver` internally; here the manager's
+     * resolver handle is passed explicitly, as on the send paths.
      *
      * **The format.** The signed digest is
      * `SHA256d(prefix ‖ varint(bytes.size) ‖ bytes)` over