Add vulnerability scanner and WebSocket manager for scan notifications

- Implemented VulnerabilityScanner class to scan images for vulnerabilities using Trivy and NVD API.
- Added methods to parse and store vulnerability data in the database.
- Created WebSocketManager class to handle real-time notifications for scan status updates.
- Integrated WebSocket notifications for scan start, completion, and failure events.

README.md

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+# GitLab Docker Images Tracker - Backend
+
+FastAPI backend for tracking Docker images across GitLab repositories with vulnerability scanning.
+
+## Setup
+
+1. Install dependencies:
+```bash
+uv sync
+```
+
+2. Set environment variables:
+```bash
+export GITLAB_TOKEN="your_gitlab_token_here"
+export GITLAB_URL="https://your-gitlab-instance.com"  # Optional, defaults to gitlab.com
+export GITLAB_GROUPS="group1,group2,group3"  # Optional, comma-separated list of group IDs or paths
+```
+
+**Group Filtering**: To limit scanning to specific GitLab groups (recommended for large instances), set the `GITLAB_GROUPS` environment variable with a comma-separated list of group IDs or paths. For example:
+- `GITLAB_GROUPS=my-team,docker-projects` (using group paths)
+- `GITLAB_GROUPS=123,456,789` (using group IDs)
+- Leave empty to scan all projects (not recommended for large instances)
+
+3. Run the application:
+```bash
+uv run python main.py
+```
+
+The API will be available at `http://localhost:5000`
+
+## Features
+
+- Project discovery from GitLab
+- Docker image parsing from Dockerfiles, docker-compose files, and CI configs
+- Vulnerability scanning with Trivy or API fallback
+- Ignore rule management
+- REST API for frontend integration
+
+## API Endpoints
+
+- `GET /dashboard` - Dashboard statistics
+- `GET /projects` - List projects
+- `GET /images` - List Docker images
+- `GET /vulnerabilities` - List vulnerabilities
+- `GET /ignore-rules` - List ignore rules
+- `POST /scan/projects` - Start project discovery scan
+- `POST /scan/vulnerabilities` - Start vulnerability scan
+
+## Configuration
+
+The application uses SQLite for data storage. The database file `gitlab_docker_tracker.db` will be created automatically on first run.