0.7.0 - React 19 upgrade, dependency updates

• Upgraded React 18 to React 19 (createRoot API, peer deps support React 18 + 19)
• Upgraded kdbush to v4
• Replaced deprecated react-loading-overlay-ts with MUI Backdrop + CircularProgress
• Fixed 5 security vulnerabilities (jsdoc, copy-webpack-plugin, webpack-dev-server)
• Updated dev tooling: webpack-cli 6, sass-loader 16, css-loader 7, style-loader 4, @testing-library/jest-dom 6