build(deps-dev): add terser-webpack-plugin as explicit dependency

webpack 5.109 replaced its terser-webpack-plugin dependency with
minimizer-webpack-plugin, so it is no longer installed transitively.
webpack.common.cjs requires it directly for the production minimizer,
which broke the build after the webpack bump.

Assisted-by: Claude Code:claude-fable-5
Signed-off-by: Andy Scherzinger <info@andy-scherzinger.de>

Author: AndyScherzinger