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/setting.py

@@ -0,0 +1,102 @@
+"""System settings model for key-value configuration storage."""
+
+from datetime import datetime, timezone
+
+from sqlalchemy.exc import IntegrityError
+
+from shopdb.extensions import db
+
+
+def _utcnow():
+    """Naive UTC now for column defaults (matches the app's naive datetime cols)."""
+    return datetime.now(timezone.utc).replace(tzinfo=None)
+
+
+class Setting(db.Model):
+    """
+    Key-value store for system settings.
+
+    Settings can be managed via the admin UI and are cached
+    for performance.
+    """
+    __tablename__ = 'settings'
+
+    settingid = db.Column(db.Integer, primary_key=True, autoincrement=True)
+    key = db.Column(db.String(100), unique=True, nullable=False, index=True)
+    value = db.Column(db.Text, nullable=True)
+    valuetype = db.Column(db.String(20), default='string')  # string, boolean, integer, json
+    category = db.Column(db.String(50), default='general')  # For grouping in UI
+    description = db.Column(db.String(255), nullable=True)
+    createddate = db.Column(db.DateTime, default=_utcnow)
+    modifieddate = db.Column(db.DateTime, default=_utcnow, onupdate=_utcnow)
+
+    def to_dict(self):
+        return {
+            'settingid': self.settingid,
+            'key': self.key,
+            'value': self.get_typed_value(),
+            'valuetype': self.valuetype,
+            'category': self.category,
+            'description': self.description,
+            'createddate': self.createddate.isoformat() + 'Z' if self.createddate else None,
+            'modifieddate': self.modifieddate.isoformat() + 'Z' if self.modifieddate else None,
+        }
+
+    def get_typed_value(self):
+        """Return value converted to its proper type."""
+        if self.value is None:
+            return None
+        if self.valuetype == 'boolean':
+            return self.value.lower() in ('true', '1', 'yes')
+        if self.valuetype == 'integer':
+            try:
+                return int(self.value)
+            except (ValueError, TypeError):
+                return 0
+        return self.value
+
+    @classmethod
+    def get(cls, key: str, default=None):
+        """Get a setting value by key."""
+        setting = cls.query.filter_by(key=key).first()
+        if setting:
+            return setting.get_typed_value()
+        return default
+
+    @staticmethod
+    def _stringify(value):
+        """Convert a value to its stored string form."""
+        if isinstance(value, bool):
+            return 'true' if value else 'false'
+        return str(value) if value is not None else None
+
+    @classmethod
+    def set(cls, key: str, value, valuetype: str = 'string', category: str = 'general', description: str = None):
+        """Set a setting value, creating if it doesn't exist.
+
+        Handles the create race: two concurrent callers can both find no row and
+        both try to INSERT the same unique key. The loser's commit raises
+        IntegrityError; we roll back, re-fetch the row the winner created, and
+        apply our value to it.
+        """
+        setting = cls.query.filter_by(key=key).first()
+        if setting:
+            setting.value = cls._stringify(value)
+            db.session.commit()
+            return setting
+
+        setting = cls(key=key, valuetype=valuetype, category=category,
+                      description=description, value=cls._stringify(value))
+        db.session.add(setting)
+        try:
+            db.session.commit()
+            return setting
+        except IntegrityError:
+            db.session.rollback()
+            # Another transaction inserted this key first; update that row.
+            setting = cls.query.filter_by(key=key).first()
+            if setting is None:
+                raise
+            setting.value = cls._stringify(value)
+            db.session.commit()
+            return setting