fix: validate Connect ServiceRequest handlers

[jrandolf]

Summary

• teach #[connect_impl] to recognize Connect 0.7 ServiceRequest<'_, Req> handler parameters
• keep validation injection for the existing OwnedView<_> handler shape
• add regression coverage for both request forms and update the README example

Root cause

The macro only matched parameter type paths ending in OwnedView. Connect 0.7 generated service impls now receive connectrpc::ServiceRequest<'_, Req>, so the macro skipped those handlers and no longer injected request validation.

Validation

• cargo test -p protovalidate-buffa --test connect_impl
• cargo fmt --all -- --check
• mise x aqua:protocolbuffers/protobuf/protoc@35.1 -- cargo clippy --workspace --all-targets -- -D warnings
• mise x aqua:protocolbuffers/protobuf/protoc@35.1 -- cargo test --workspace --all-targets