dsh-cake-pan: Cake Pan Conversion

DSH Harness promotes the “everything is a plugin” philosophy. dsh-cake-pan is a client-side plugin focused on converting cake pan sizes. Implemented purely in Node.js with no network dependencies, it performs precise calculations based on input parameters. Installation requires official commands and a compatible environment for `@deepseek-ai/cordis` and `@deepseek-ai/dsh-tools`. Developers can safely use this plugin for baking size conversions.