Implement mcgibs FastMCP server for NASA GIBS
Complete implementation of all modules:
- constants.py: GIBS API endpoints, projections, TileMatrixSet defs
- models.py: Pydantic models for layers, colormaps, geocoding
- geo.py: Nominatim geocoding with rate limiting and caching
- capabilities.py: WMTS GetCapabilities XML parser with search
- colormaps.py: Colormap v1.3 parser with natural-language summaries
- client.py: Async GIBS HTTP client wrapping all API interactions
- server.py: FastMCP 3.0 tools, resources, and prompts
11 MCP tools, 3 resources, 2 prompts. 47 tests, all passing.