docs: add CHANGELOG.md with v1.0.0 release notes and unreleased roadmap

Author: DHANUSHGCODE

CHANGELOG.md

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+# Changelog
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+---
+
+## [v1.0.0] - 2026-02-19
+
+### Added
+- Real-time log ingestion API via FastAPI with `/logs/` and `/predict/` endpoints
+- Isolation Forest unsupervised anomaly detection model (scikit-learn)
+- AI model training script `ai-model/train_model.py` with synthetic log data generation
+- SQLite database with SQLAlchemy ORM for persistent log storage
+- Next.js 15 + React 18 interactive security dashboard
+- Recharts integration for traffic spike and threat distribution visualizations
+- 3D Threat Globe visualization using React Three Fiber and Three.js
+- 3D Network Topology Graph with real-time interactive nodes
+- TailwindCSS utility-first styling across all frontend components
+- Docker & `docker-compose.yml` for containerized full-stack deployment
+- `.dockerignore` for optimized Docker image builds
+- GitHub Actions CI/CD pipeline with PYTHONPATH fix for backend module imports
+- Comprehensive unit tests for `/logs/` API endpoints
+- `CONTRIBUTING.md` with contribution guidelines
+- `SECURITY.md` with security policy and responsible disclosure process
+- `SETUP_GUIDE.md` with step-by-step local setup instructions
+- `github_deploy_guide.md` with deployment instructions
+- MIT License
+- Repository topics: python, docker, machine-learning, nextjs, cybersecurity, anomaly-detection, isolation-forest, threat-detection, security-monitoring, fastapi
+
+### Fixed
+- Frontend downgraded from unstable Next.js canary to stable Next.js 15 + React 18 to resolve compatibility issues
+- CI pipeline: set `PYTHONPATH=.` to resolve backend module import errors in tests
+- `.gitignore` updated to exclude debug, temporary, and compiled files
+
+### Architecture
+- Backend: Python 3.10+, FastAPI, scikit-learn, Pandas, NumPy, SQLAlchemy, SQLite
+- Frontend: Next.js 15, React 18, TailwindCSS, Recharts, Three.js, React Three Fiber, @react-three/drei, Lucide React
+- DevOps: Docker, GitHub Actions CI
+
+---
+
+## [Unreleased]
+
+### Planned
+- WebSocket integration for live real-time threat alerts
+- OAuth2 user authentication and role-based access control
+- Cloud deployment to AWS / Render
+- PostgreSQL migration support for production-scale databases
+- Additional ML models (Autoencoder, ensemble methods) for improved detection accuracy