fix: validate chunk order and identity when deserializing chunked transactions - #2736

Description:

Transaction.from_bytes() accepted a TransactionList for a chunked transaction (FileAppendTransaction, TopicMessageSubmitTransaction) whose chunk groups were reordered or belonged to different chunked transactions. The restored transaction then re-serialized and executed the chunks in input order: file contents were appended out of order, and topic message chunks were submitted out of sequence.

• Validate the chunk groups of chunked transaction types:
  • all chunk transaction IDs share the same payer account;
  • transactionValidStart strictly increases from one chunk group to the next;
  • consensusSubmitMessage only: chunkInfo.number is the chunk's 1-based position, chunkInfo.total equals the number of chunk groups, and chunkInfo.initialTransactionID equals the first chunk's transaction ID.
• from_bytes() only falls back to the single Transaction format when the bytes do not decode to a non-empty TransactionList. Validation errors now reach the caller as a ValueError with the real cause, instead of being replaced by an unrelated parse error.
• Split the private _process_transaction_list_bytes() into _parse_transaction_list() and _process_transaction_list(). No public API changes.

Related issue(s):

Fixes #2710

Notes for reviewer:

• Root cause: transaction_ids is collected in first-seen input order, and _validate_transaction_pairs() builds its expected layout from it, so a reordered list always matched itself. The new checks read each chunk group's own transactionID and chunkInfo instead.
• Reject, don't sort: malformed lists are rejected, not silently reordered.
• Strictly increasing, not an exact +1ns step: Java and the JS TopicMessageSubmitTransaction space chunk valid starts 1ns apart, but the JS FileAppendTransaction uses a configurable chunkInterval (default 10ns). Neither carries nanos overflow into seconds, so valid starts are compared as (seconds, nanos).
• Single-chunk topic messages: Python and Java omit chunkInfo for a single chunk, while JS sets total=1, number=1. Both are accepted. A lone chunk of a larger message (e.g. total=2) is now rejected as incomplete.
• Bodies without node account IDs: the chunk checks also run on this path, which previously skipped chunk validation entirely.
• Known limit: FileAppendTransaction carries no chunk count, so a list with its last chunk(s) removed cannot be detected. Topic messages are covered by chunkInfo.total.
• Updated existing tests: four tests built chunk sequences that are now invalid; they now use sequential chunk IDs:
  • test_validate_transaction_bodies_chunk_transaction and test_validate_transaction_bodies_chunk_transaction_mutiple_node_ids used different payers (0.0.2 and 0.0.3);
  • test_validate_transaction_bodies_for_chunk_file_append_tx and test_validate_transaction_bodies_for_chunk_message_submit_tx built chunk IDs with TransactionId.generate(), which subtracts a random 5–8s, so the second chunk was often earlier than the first. The topic test also gave both chunks number=1 and unrelated initialTransactionIDs.
• Fixed the transaction_ids annotation in _process_transaction_list() (list[Transaction] → list[TransactionId]).
• Tests & Linters:
  • New tests/unit/chunked_transaction_from_bytes_test.py (66 cases) tests through Transaction.from_bytes() for both types, with one and two nodes:
    • round-trips of 1–3 chunks, signed and unsigned, give identical bytes, and 10ns chunk spacing is accepted;
    • swapped chunk groups, different payers, non-increasing valid starts, wrong chunkInfo.number/total, mismatched initialTransactionID, missing chunkInfo and an incomplete topic message are rejected with a specific message. All 34 rejection cases fail against main.
  • New tests in transaction_freeze_and_bytes_test.py for the single Transaction fallback (previously untested) and for a TransactionList validation error reaching the caller.
  • uv run pytest tests/unit: 3404 passed.
  • All pre-commit hooks (gitleaks, end-of-file-fixer, trailing-whitespace, ruff-check, ruff-format, bandit) pass.
  • Integration tests have not been run locally.

Checklist

• Documented (Code comments, README, etc.)
• Tested (unit, integration, etc.)