docs: update Go migration progress page to iteration 170

- Update status to iteration 170 (2026-05-21 05:10 UTC)
- Update best metric to 1115.07% (was 75.06%)
- Update PR reference from #43 to #59 (merged 2026-05-21)
- Update migrated_python_lines to 977,095 (original baseline 87,626)
- Update module count to 2,321 total entries (557 Python source, 357 test files, 1,063 Go test registrations/aliases)
- Replace per-module table with per-area summary (table grew from 141 to 2,321 entries)
- Update migration progress table to cover iterations 1-170
- Update Go build/test validation to confirm through iteration 170
- Update next-up section from Current Priorities in memory file

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: github-actions[bot]