Guard Forknote parent blockchain branch depth

[MoneroOcean]

Motivation

• Prevent an attacker-controlled merge-mining depth (read from tx_extra as an untrusted varint) from driving an unchecked std::vector::resize during deserialization which can OOM or abort the process.
• The unsafe path is reachable because parent block parsing for v2/v3 blocks deserializes a merge-mining tag and uses its depth directly to size the blockchain_branch vector.
• Ensure deserialization validates the claimed depth against the remaining input before any allocation occurs.

Description

• Add load/save-aware helper templates has_enough_blockchain_branch_bytes(Archive&, size_t, ...) that return true for saving and perform a remaining-bytes check for loading.
• Invoke the load-side check immediately before PREPARE_CUSTOM_VECTOR_SERIALIZATION(mm_tag.depth, ...) so deserialization returns false when mm_tag.depth claims more crypto::hash entries than remain.
• Change implemented in src/cryptonote_basic/cryptonote_basic.h (helper templates + early validation before resizing blockchain_branch).

Testing

• Ran git diff --check which completed successfully and showed no whitespace/style issues.
• Attempted npm install --no-audit --no-fund --no-package-lock to build the native addon and run tests, but the run was blocked by the npm registry returning 403 Forbidden, so the native build/tests could not be executed in this environment.
• Attempted a C++ syntax-only check with g++ -std=c++17 -I src -I src/contrib/epee/include -fsyntax-only src/cryptonote_basic/cryptonote_format_utils.cpp, but local compilation was prevented by missing Boost headers and restricted apt-get access in the runner environment.

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Codex Task