fix(crypto): harden crypto module security and robustness

[Federico2014]

What does this PR do?

This PR hardens the security and robustness of the crypto module across five areas:

1. Remove unused topicsList from shielded TRC20 log APIs

   • Removed the topicsList field from ScanShieldedTRC20NotesByIvk and
     ScanShieldedTRC20NotesByOvk API responses, as it was never populated
     and exposed misleading empty data.
   • Updated api.proto, RpcApiService, HTTP servlet handlers, and Wallet
     accordingly.
   • api.proto removes the topicsList field from shielded TRC20 scan
     responses. This field was never populated by the server (always returned
     empty), so existing clients will see no behavioral difference.
   • Added full gRPC service test coverage in RpcApiServicesTest.

2. Shielded transaction API security enhancement

   • Strengthened parameter validation in Wallet for shielded transaction
     builders (ZenTransactionBuilder, ShieldedTRC20ParametersBuilder).
   • sprout-verifying.key removed from the repository root; the file was
     not referenced by any code and its presence in source control was
     unnecessary.
   • Changed the default value of allowShieldedTransactionApi from true
     to false to reduce exposure by default, since some shielded transaction
     APIs require passing private keys as parameters. Updated config.conf
     with an explicit warning advising users to only invoke these APIs locally.
   • Added ShieldedTransferActuatorTest and ArgsTest to cover new
     validation paths.

3. SM2 deterministic signing and robustness (SM2Signer.java)

   • Replaced RandomDSAKCalculator with HMacDSAKCalculator for
     deterministic nonce generation (RFC 6979 equivalent), eliminating
     nonce-reuse risk from the random K path.
   • Added null/empty guards on all public entry points (init,
     generateSM3Hash, generateHashSignature, verifySignature,
     verifyHashSignature, calculateE).
   • Fixed misleading error message that referred to "ECDSA" instead of "SM2".
   • Extended SM2KeyTest with additional edge-input cases.

4. ECKey input validation (ECKey.java)

   • Added strict null and length checks on fromPrivate, fromPublicOnly,
     and recovery APIs, preventing silent truncation of oversized key material.
   • Expanded ECKeyTest with negative test cases for invalid inputs.

5. Signature and private key validation (Rsv.java, SignUtils.java,
   WitnessInitializer.java)

   • Added range checks for r, s, v components in Rsv.
   • Enforced key material validity in SignUtils before signing.
   • Hardened WitnessInitializer to reject malformed private keys on node
     startup.

Why are these changes required?

The existing crypto code lacked defensive validation at API and library
boundaries, creating exposure to:

• Nonce reuse in SM2 (non-deterministic random K path)
• Silent acceptance of invalid or truncated key material in ECKey
• Missing range checks on signature components (r, s, v)
• Information leakage through unused protobuf fields in shielded APIs
• Risk of private key leakage when shielded transaction APIs are enabled
  by default on public-facing nodes

These issues were identified during an internal security review of the
crypto module.

This PR has been tested by:

• Unit Tests — ECKeyTest, SM2KeyTest, WalletMockTest,
  RpcApiServicesTest, ShieldedTransferActuatorTest, ArgsTest,
  WitnessInitializerTest
• Build passes (./gradlew clean build -x test)
• Manual testing on private testnet

Extra details

• Breaking change: nodes that relied on allowShieldedTransactionApi
  defaulting to true must now explicitly set it in config.conf.
• No changes to consensus logic or on-chain state transitions.