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/usb/migrations/versions/0001_usb_anchor.py

@@ -0,0 +1,28 @@
+"""usb 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_usb. From this
+anchor forward, new usb 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 = 'usb0001anchor'
+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

plugins/usb/migrations/versions/0002_drop_checkout_machineid.py

@@ -0,0 +1,42 @@
+"""Drop the dead usbcheckouts.machineid column (ADR-001: Machine retired).
+
+machineid was a NOT NULL soft-reference to the retired machines table; every
+new checkout stored the sentinel 0. It has no FK, no meaning under the asset
+model, and no reader. Drop it.
+
+Idempotent (skips a missing table/column). Downgrade restores it NOT NULL with
+server_default 0 so any existing rows stay valid.
+
+Revision ID: usb0002dropmachineid
+Revises: usb0001anchor
+"""
+from alembic import op
+import sqlalchemy as sa
+
+
+revision = 'usb0002dropmachineid'
+down_revision = 'usb0001anchor'
+branch_labels = None
+depends_on = None
+
+
+def upgrade():
+    bind = op.get_bind()
+    insp = sa.inspect(bind)
+    if 'usbcheckouts' not in insp.get_table_names():
+        return
+    cols = {c['name'] for c in insp.get_columns('usbcheckouts')}
+    if 'machineid' in cols:
+        op.drop_column('usbcheckouts', 'machineid')
+
+
+def downgrade():
+    bind = op.get_bind()
+    insp = sa.inspect(bind)
+    if 'usbcheckouts' not in insp.get_table_names():
+        return
+    cols = {c['name'] for c in insp.get_columns('usbcheckouts')}
+    if 'machineid' not in cols:
+        op.add_column('usbcheckouts',
+                      sa.Column('machineid', sa.Integer(), nullable=False,
+                                server_default='0'))