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>

Cargo.lock

@@ -615,6 +615,7 @@ version = "0.1.0"
 dependencies = [
  "axum",
  "base64",
+ "bson",
  "chrono",
  "compliance-core",
  "dioxus",
@@ -638,6 +639,7 @@ dependencies = [
  "tower-sessions",
  "tracing",
  "url",
+ "uuid",
  "web-sys",
 ]