nimiq-blockchain is missing a wall-clock upper bound on block timestamps

### Impact Block timestamp validation enforces that `timestamp >= parent.timestamp` for non-skip blocks and `timestamp == parent.timestamp + MIN_PRODUCER_TIMEOUT` for skip blocks, but there is no visible upper bound check against the wall clock. A malicious block-producing validator can set block timestamps arbitrarily far in the future. This directly affects reward calculations via `Policy::supply_at()` and `batch_delay()` in `blockchain/src/reward.rs`, inflating the monetary supply beyond the intended emission schedule. ### Patches TBD ### Workarounds No know workarounds. Source Code Location: https://github.com/nimiq/core-rs-albatross Affected Packages: - rust:nimiq-blockchain, affected <= 1.3.0 CWEs: - CWE-20: Improper Input Validation - CWE-1284: Improper Validation of Specified Quantity in Input CVSS: - Primary: score 9.1, CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H - CVSS_V3: score 9.1, CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H References: - https://github.com/nimiq/core-rs-albatross/security/advisories/GHSA-49xc-52mp-cc9j - https://nvd.nist.gov/vuln/detail/CVE-2026-40093 - https://github.com/advisories/GHSA-49xc-52mp-cc9j