Upgrade allow adding image in ticket details page comment section

app/models.py

@@ -308,4 +308,49 @@ class KBAttachment(db.Model):
         return f'/admin/kb/files/{self.stored_name}'
 
     def __repr__(self):
-        return f'<KBAttachment {self.filename}>'
+        return f'<KBAttachment {self.filename}>'
+
+
+class SystemSetting(db.Model):
+    """Key-value store for application-wide configuration flags.
+
+    Values are persisted as strings; helper class methods handle
+    typed access so callers never touch raw strings directly.
+    """
+    __tablename__ = 'system_settings'
+
+    id          = db.Column(db.Integer, primary_key=True)
+    key         = db.Column(db.String(100), unique=True, nullable=False, index=True)
+    value       = db.Column(db.String(500), nullable=False)
+    description = db.Column(db.String(256))
+    updated_at  = db.Column(db.DateTime, default=datetime.utcnow, onupdate=datetime.utcnow)
+
+    @classmethod
+    def get(cls, key, default=None):
+        """Return the raw string value for *key*, or *default* if absent."""
+        row = cls.query.filter_by(key=key).first()
+        return row.value if row else default
+
+    @classmethod
+    def get_bool(cls, key, default=True):
+        """Return the value for *key* coerced to bool."""
+        raw = cls.get(key)
+        if raw is None:
+            return default
+        return raw.lower() in ('1', 'true', 'yes', 'on')
+
+    @classmethod
+    def set(cls, key, value, description=None):
+        """Upsert *key* = *value*.  Caller is responsible for committing."""
+        row = cls.query.filter_by(key=key).first()
+        if row:
+            row.value = str(value)
+            if description is not None:
+                row.description = description
+        else:
+            row = cls(key=key, value=str(value), description=description)
+            db.session.add(row)
+        return row
+
+    def __repr__(self):
+        return f'<SystemSetting {self.key}={self.value}>'