feat: add MCP servers dashboard page with CRUD and token management

New page at /mcp-servers to register, view, and manage MCP server
instances. Shows endpoint config, enabled tools, and access tokens
with reveal/regenerate controls. Includes McpServerConfig model in
compliance-core, MongoDB collection accessor, server functions for
list/add/delete/regenerate-token, sidebar nav entry, and full CSS.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

compliance-dashboard/src/pages/mod.rs

@@ -10,6 +10,7 @@ pub mod graph_explorer;
 pub mod graph_index;
 pub mod impact_analysis;
 pub mod issues;
+pub mod mcp_servers;
 pub mod overview;
 pub mod repositories;
 pub mod sbom;
@@ -27,6 +28,7 @@ pub use graph_explorer::GraphExplorerPage;
 pub use graph_index::GraphIndexPage;
 pub use impact_analysis::ImpactAnalysisPage;
 pub use issues::IssuesPage;
+pub use mcp_servers::McpServersPage;
 pub use overview::OverviewPage;
 pub use repositories::RepositoriesPage;
 pub use sbom::SbomPage;