Enhance MobileLLM-R1 project page with detailed training pipeline and architecture sections

- Added comprehensive descriptions of the training pipeline phases, including Pre-training, Mid-training, and Post-training, with insights into data sources and methodologies.
- Introduced a new Technical Architecture section detailing model specifications and key design features for the MobileLLM-R1 models.
- Enhanced visual elements and tooltips for better user engagement and understanding of the model's capabilities and performance metrics.
- Included a Data Curation Methodology section outlining the strategies for optimizing training data and its impact on reasoning capabilities.

Author: vukrosic