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/Cargo.toml

@@ -34,6 +34,8 @@ server = [
     "dep:url",
     "dep:sha2",
     "dep:base64",
+    "dep:uuid",
+    "dep:bson",
 ]
 
 [dependencies]
@@ -67,3 +69,5 @@ rand = { version = "0.9", optional = true }
 url = { version = "2", optional = true }
 sha2 = { workspace = true, optional = true }
 base64 = { version = "0.22", optional = true }
+uuid = { workspace = true, optional = true }
+bson = { version = "2", features = ["chrono-0_4"], optional = true }