Replace README with minimal version (GitHub link + citation)

README.md

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+📄 GitHub: https://github.com/thanhdath/finer-sql
+
+## Citation
+
+```bibtex
+@inproceedings{finersql,
+  author       = {Thanh Dat Hoang and Thanh Trung Huynh and Matthias Weidlich and Thanh Tam Nguyen and Tong Chen and Hongzhi Yin and Quoc Viet Hung Nguyen},
+  title        = {Boosting Small Language Models for Text-to-SQL with Fine-Grained Execution Feedback and Cost-Efficient Rewards},
+  booktitle    = {ICDE},
+  publisher    = {IEEE},
+  year         = {2026},
+}
+```