Initial import: shopdb-flask multi-site asset platform

Flask + Vue rewrite of the classic-ASP shopdb, built as a plugin
framework so sister GE Aerospace sites can adopt it. Product version
0.7.0-pre-0.8.0, plugin contract 0.11.0, 966 backend tests.

Key entry points:
- docs/INSTALL-WINDOWS-IIS.md - tested Windows + IIS install runbook
  (own-site and subpath deployment methods)
- docs/PILOT-DEPLOY.md - production pilot: stand up + import + verify
- docs/IMPORT-API.md - schema-agnostic legacy data import contract
- scripts/site_imports/wjf/ - West Jefferson reference import loader
- docs/adr/ - twelve accepted architecture decision records

migrations/DATA_MIGRATION_GUIDE.md

@@ -0,0 +1,13 @@
+# Legacy data migration (superseded)
+
+The direct-database migration this guide used to describe is retired. Legacy
+data now enters through the HTTP import surface, which runs authorization,
+validation, auditing, and plugin hooks on every row:
+
+- Contract: the IMPORT-API wiki page (admin API token + `X-Import-Mode: true`,
+  which preserves original created/modified timestamps).
+- Adoption playbook for a new site: the IMPORT-ADOPTION wiki page.
+- Worked reference loader (West Jefferson classic-ASP schema, 15 stages,
+  idempotent and resumable): `scripts/site_imports/wjf/`.
+- Full pilot sequence (stand up + import + verify + cutover):
+  the PILOT-DEPLOY wiki page.