fix(compiler): validate rpc request/response types

[retryoos]

Summary

• Add schema validation for service RPC request/response types in the compiler IR validator.
• Extend FDL/Proto/FBS service tests so RPCs with unknown request/response types now fail validation.
• Document service RPC type validation in the compiler guide and add a small service.fdl example plus a foryc usage snippet.

Technical details

• SchemaValidator._check_type_references now also walks schema.services and verifies that each RpcMethod.request_type and RpcMethod.response_type resolves via schema.get_type(...). If a type is missing, it reports Unknown type 'X' at the RPC location.
• New tests:
  • test_service_unknown_request_type_fails_validation,
    test_service_unknown_response_type_fails_validation,
    test_service_known_types_pass_validation in test_fdl_service.py (one test also asserts that the error carries a non-null location).
  • Matching unknown-type validation tests in test_proto_service.py and test_fbs_service.py to cover the Proto and FlatBuffers frontends feeding into the shared IR.
• Docs:
  • docs/compiler/compiler-guide.md now mentions that RPC request/response types are validated like other type references, and includes a foryc compiler/examples/service.fdl --java_out=... --python_out=... example.
• Example:
  • compiler/examples/service.fdl defines HelloRequest, HelloReply, and a Greeter service with a unary SayHello RPC.

Testing

Locally on macOS:

cd compiler

python -m pytest fory_compiler/tests/test_fdl_service.py -v
python -m pytest fory_compiler/tests/test_proto_service.py -v
python -m pytest fory_compiler/tests/test_fbs_service.py -v
python -m pytest fory_compiler/tests/ -v