test: add contract-side coverage for maxAutomaticTokenAssociations = -1

[Dosik13]

Description:

Add tests for the HIP-904 "unlimited" auto-association sentinel (-1) on the
contract entry points. The value already round-trips and works today, but only
the account path was tested — the contract path (including the Int32Value
wrapper on update and the != 0 sentinel guard in the flow) was unverified.
Additive tests only; no production change.

• Add ContractCreateTransaction unit test — -1 survives the proto round-trip as a plain int32
• Add ContractUpdateTransaction unit test — -1 survives inside the Int32Value wrapper (wrapper non-nil)
• Add ContractCreateFlow unit test — -1 propagates to the inner create tx, pinning the != 0 guard
• Add e2e test — a contract created with -1 auto-associates two distinct fungible tokens with no explicit association
• Add e2e test — ContractUpdateTransaction to -1, verified via ContractInfoQuery

Related issue(s):

Fixes #1778

Checklist

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

[lfdt-bot]

✅ Snyk checks have passed. No issues have been found so far.

Status	Scan Engine	Critical	High	Medium	Low	Total (0)
✅	Open Source Security	0	0	0	0	0 issues

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
see 4 files with indirect coverage changes

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