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

shopdb/core/models/model.py

@@ -0,0 +1,43 @@
+"""Model (vendor catalog model number) model."""
+
+from shopdb.extensions import db
+from .base import BaseModel
+
+
+class Model(BaseModel):
+    """Vendor catalog model information (machines, PCs, printers, network)."""
+    __tablename__ = 'models'
+
+    modelnumberid = db.Column(db.Integer, primary_key=True)
+    modelnumber = db.Column(db.String(100), nullable=False)
+
+    # Link to model type (what kind of thing this catalog model is for)
+    modeltypeid = db.Column(
+        db.Integer,
+        db.ForeignKey('modeltypes.modeltypeid'),
+        nullable=True
+    )
+
+    # Link to vendor/manufacturer
+    vendorid = db.Column(
+        db.Integer,
+        db.ForeignKey('vendors.vendorid'),
+        nullable=True
+    )
+
+    description = db.Column(db.Text)
+    imageurl = db.Column(db.String(500), comment='URL to product image')
+    documentationurl = db.Column(db.String(500), comment='URL to documentation')
+    notes = db.Column(db.Text)
+
+    # Relationships
+    modeltype = db.relationship('ModelType', backref='models')
+    vendor = db.relationship('Vendor', backref='models')
+
+    # Unique constraint on modelnumber + vendor
+    __table_args__ = (
+        db.UniqueConstraint('modelnumber', 'vendorid', name='uq_model_vendor'),
+    )
+
+    def __repr__(self):
+        return f"<Model {self.modelnumber}>"