[Frontend] Add contract-schema compatibility checks to CI

## Problem
The frontend can compile while using stale field names, enum values, or transaction parameters relative to the deployed contract and backend schemas.

## Scope
Compare checked-in client types/ABI artifacts with the canonical contract interface and fail on incompatible changes.

## Acceptance criteria
- CI verifies read/write method names, argument types, error/event identifiers, and network addresses.
- Additions are allowed with an explicit compatibility report; removals and type changes fail.
- A fixture test exercises pet registration, access sharing, and ownership transfer end to end against a local/test deployment.
- The check is reproducible without downloading an unpinned schema.
- Failure output identifies the consumer file and remediation.

Start by locating the checked-in client types and ABI artifacts, then identify the canonical contract interface and current CI entry point. Review how a local or test deployment can exercise pet registration, access sharing, and ownership transfer. Done means reproducible CI checks report additions, reject removals or type changes, and identify the consumer file and remediation.

Written by the indexing model from the issue text.