Refactor nav: remove numbers from Tools/Settings, add separator and Tasks item

- Remove "6." / "7." prefixes from Tools and Settings nav labels and page titles
- Add a horizontal separator (nav-sep) before the Tools/Settings group
- Move Tasks into the nav as a regular nav-item after the separator,
  replacing the separate tasks-nav-btn at the sidebar bottom
- Tasks item retains the active-count badge (tasks-nav-count)

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

audit/internal/webui/pages.go

@@ -44,11 +44,11 @@ func renderPage(page string, opts HandlerOptions) string {
 		body = renderEndurance(opts)
 	case "tools":
 		pageID = "tools"
-		title = "6. Tools"
+		title = "Tools"
 		body = renderTools()
 	case "settings":
 		pageID = "settings"
-		title = "7. Settings"
+		title = "Settings"
 		body = renderSettings(opts)
 	// Legacy routes (redirected at HTTP level in handlePage; these are fallbacks)
 	case "validate", "tests":