Add pdf-mcp package (I-CAN-hack/pdf-mcp)

MCP server for reading, rendering, and searching PDF files using PyMuPDF.
Exposes get_page_text, get_page_image (render page as PNG), search_text.
Python, so it spawns reliably under the mcp-gateway stdio backend.

packages/default.nix

@@ -29,5 +29,6 @@
   ovhcloud-mcp = pkgs.callPackage ./ovhcloud-mcp/package.nix { };
   slskd-mcp = pkgs.callPackage ./slskd-mcp/package.nix { };
   yarr = pkgs.callPackage ./yarr/package.nix { };
+  pdf-mcp = pkgs.callPackage ./pdf-mcp/package.nix { };
   # example-mcp-server = pkgs.callPackage ./example-mcp-server/package.nix { };
 }