Change from_timestamp type from u32 to u64

Updated the from_timestamp parameter from Option<u32> to Option<u64> in asset, notification, and transaction APIs and client methods to support larger timestamp values and prevent potential overflows.

Use Cargo NDK Gradle plugin from Maven Central (#896)

use publishReleasePublicationToSonatypeRepository

Conditionally enable signing in build script

Added a check to enable signing only if MVN_SIGNING_KEY and MVN_SIGNING_PASSPHRASE environment variables are set. This prevents build failures when signing credentials are not provided.

Add Maven Central publish step to Android release workflow

The release workflow now includes a separate step to publish Android artifacts to Maven Central using a new justfile recipe. The existing publish step for GitHub Packages was renamed for clarity and now only targets GPR.

Add serialization for TransferNFT in TransactionType

Added serde and strum serialization attributes to the TransferNFT variant in the TransactionType enum to ensure correct naming during serialization and deserialization.

Add referral risk scoring and risk signals tracking

Introduces a risk scoring system for referrals, including new models, database tables, and logic to evaluate and store risk signals. Referral attempts and uses now reference risk signals instead of raw IP addresses, and rate limiting is handled via database queries rather than cache. Updates API, storage, and gem_rewards crates to support risk scoring, configuration, and leaderboard changes.

Refactor nack handling to use requeue parameter

Consolidated nack and nack_requeue methods into a single nack method with a requeue parameter. Updated call sites to use the new method, simplifying error handling and reducing code duplication.

Add rewards level support to usernames and rewards

Introduces the RewardLevel enum and related database table, updates the usernames table and model to include rewards level, verification, and enablement fields, and extends the rewards logic and repository to handle these new fields. Also updates related SQL migrations and schema, and refactors code for improved clarity and consistency.

Improve typed data parsing in Ethereum handler

Enhanced the parse_sign_typed_data method to handle non-string typed data by serializing it to JSON. Added a test to verify parsing of EIP-712 typed data for Hyperliquid use case. Minor formatting update in Tron preload_mapper test helper.