Fix issues #1, #3, #5: misc improvements

- #5: Unwrap _brand.yml for Quarto 1.9+ compatibility (remove top-level
  brand: wrapper so meta/logo/color/typography are at the top level)
- #1: Add quiet parameter to na_sum() to suppress warnings in loops/pipelines
- #3: Add beep() function for CLI beep, desktop notifications, and webhook
  alerts (supports type=beep|notify|webhook|all)

tests/testthat/test_utils.R

@@ -58,6 +58,12 @@ test_that("na_sum fails with non-numerics", {
   expect_error(na_sum(as.factor(1:10)))
 })
 
+test_that("na_sum quiet=TRUE suppresses the message", {
+  expect_message(na_sum(c(1:10, NA)), "Taking a sum")
+  expect_silent(na_sum(c(1:10, NA), quiet = TRUE))
+  expect_equal(na_sum(c(1:10, NA), quiet = TRUE), 55)
+})
+
 
 context("Test Utilities - Pretty Count")