Add EduScale SPAN 2x and 3x TensorFlow Lite models and supporting documentation and benchmark data. Files added: models/eduscale_span_x2.tflite, models/eduscale_span_x3.tflite, docs/MODEL_CARD.md, docs/DATASET_CARD.md, benchmarks/benchmark_x2.csv, benchmarks/benchmark_x3.csv, benchmarks/benchmark_summary.csv. README.md was expanded to describe the project, intended use, repository structure, benchmark summary, usage example, data sources, and license (Apache-2.0). Benchmarks provide per-image metrics and a short summary for mobile runtime evaluation.
