Fix stale CN input length causing OOB reads

[MoneroOcean]

Motivation

• Prevent a memory-safety and PoW-correctness bug in the CN path where m_input_cn_len could remain stale when consecutive jobs reuse the same algo/seed/mem configuration, leading to memcpy() reading past the decoded blob.

Description

• Update m_input_cn_len immediately after decoding and validating inputs for every non-RX job and remove the redundant assignment from the reconfiguration-only branch so CN copying and hashing always use the current blob length (moner-job.cpp).

Testing

• Ran npm test, but the native addon build could not complete because fetching the nan dependency from npm was blocked with HTTP 403, so the test suite could not execute (no automated tests passed in this environment).

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Codex Task