Add operations dashboard and build stock checks

[yusufm]

Summary

• consolidate dashboard/reporting into one operations dashboard with stockroom, reorder, build activity, and data-health signals
• add read-only build stock checks and manifest/source/file visibility for revisions
• preserve compatibility for BOM traversal, legacy revision snapshots, and new API error behavior

Verification

• venv/bin/python -m py_compile web/app.py smallfactory/core/v1/entities.py
• venv/bin/python -m pytest

Result: 422 passed, 1 skipped