[Discovery] context7 - Library Documentation

## Project Association

This issue tracks the `context7` MCP server in the core profile.

### Server Details
- **Name**: context7
- **Source**: https://github.com/upstash/context7
- **Docker Hub**: https://hub.docker.com/r/mcp/context7
- **Category**: docs
- **Language**: TypeScript/Node.js

### Transport Status
- **Current**: Native HTTP support (`MCP_TRANSPORT=http`)
- **Implementation**: No wrapper needed
- **Docker Image**: `mcp/context7:latest`

### Tools Provided
- `resolve-library-id`: Get Context7-compatible library ID
- `get-library-docs`: Fetch documentation for a library

### Docker Status
- Official image: `mcp/context7`
- No custom build needed
- HADOLint: N/A (official image)

### Notes
- Provides up-to-date, version-specific documentation
- Optional `CONTEXT7_API_KEY` for higher rate limits (60 req/hr without)
- Native HTTP transport on port 8080

### Tracking
- [ ] Document library coverage
- [ ] Test rate limiting behavior
- [ ] Consider caching strategy