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

plugins/knowledgebase/migrations/versions/0001_knowledgebase_anchor.py

@@ -0,0 +1,28 @@
+"""knowledgebase plugin anchor (ownership cutover).
+
+Stamp-only no-op. The core Alembic chain (baseline .. 7d16_directoryemployees)
+already created every table this plugin owns at the cutover point, so there is
+nothing to build here. This revision gives the plugin's own chain a base that
+`flask plugin upgrade-all` can stamp into alembic_version_knowledgebase. From this
+anchor forward, new knowledgebase schema changes land as 000N revisions in this
+directory, never in the core chain. See ADR-008.
+"""
+from alembic import op  # noqa: F401
+import sqlalchemy as sa  # noqa: F401
+
+
+# revision identifiers, used by Alembic.
+revision = 'knowledgebase0001anchor'
+down_revision = None
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    # No-op: the core chain owns every table that exists at the cutover.
+    pass
+
+
+def downgrade():
+    # No-op: this anchor never unwinds core-owned tables.
+    pass