fix(server): encode V2 response IntegrityIds

[gijzelaerr]

Summary

• append the current per-client read or write IntegrityId to every established-session V2 response
• preserve the legacy V1 response layout
• preserve the current server's optional TCP-reset behavior after symbolic reads
• cover read/write counter selection and sequential V2 TLS operations

The branch now includes current master through a merge commit; its previous conflicts are resolved without rewriting history.

Verification

• uv run --frozen --extra test --extra s7commplus pytest -q (1779 passed, 82 skipped)
• focused V2/TLS/server tests (124 passed)
• uv run --frozen pre-commit run --all-files
• uv build --no-sources

Fixes #802