feat: rebrand logos with wordmark/mark variants and pipe-friendly API

- Replace old civilytics_logo.png/white.png/jpg/pdf with new rebrand
  assets: civilytics-wordmark.png, civilytics-wordmark-reverse.png,
  civilytics-mark.png, civilytics-mark-reverse.png (all transparent bg)
- make_logo_grob() now accepts type = c("wordmark", "mark") alongside
  variant = c("light", "dark") for 4 combinations
- New civilytics_logo() pipe-friendly convenience function:
    ggplot(df, aes(x, y)) + geom_point() + theme_civilytics() |>
      civilytics_logo()
  R's |> has lower precedence than +, so the full ggplot chain pipes
  through without parentheses
- Remove old icon/favicon assets no longer used
- Wrap showtext-dependent examples in \dontrun{} to prevent R CMD check
  failures in headless PostScript environments

tests/testthat/test_theme.R

@@ -160,20 +160,43 @@ test_that("theme_civilytics_dark uses navy for strip background", {
 
 # --- make_logo_grob ----------------------------------------------------------
 
-test_that("make_logo_grob returns a gg object for light variant", {
-  logo <- make_logo_grob("light")
-  expect_s3_class(logo, "gg")
+test_that("make_logo_grob returns a gg object for all type/variant combos", {
+  for (type in c("wordmark", "mark")) {
+    for (variant in c("light", "dark")) {
+      logo <- make_logo_grob(type = type, variant = variant)
+      expect_s3_class(logo, "gg")
+    }
+  }
 })
 
-test_that("make_logo_grob returns a gg object for dark variant", {
-  logo <- make_logo_grob("dark")
-  expect_s3_class(logo, "gg")
-})
-
-test_that("make_logo_grob defaults to light variant", {
+test_that("make_logo_grob defaults to wordmark light", {
   expect_no_error(make_logo_grob())
 })
 
+test_that("make_logo_grob errors on invalid type", {
+  expect_error(make_logo_grob(type = "banner"))
+})
+
 test_that("make_logo_grob errors on invalid variant", {
-  expect_error(make_logo_grob("purple"))
+  expect_error(make_logo_grob(variant = "purple"))
+})
+
+# --- civilytics_logo (pipe-friendly) -----------------------------------------
+
+test_that("civilytics_logo returns a grob", {
+  p <- ggplot(mpg, aes(displ, hwy)) + geom_point() + theme_civilytics()
+  result <- suppressWarnings(civilytics_logo(p))
+  expect_s3_class(result, "grob")
+})
+
+test_that("civilytics_logo works with pipe operator", {
+  p <- ggplot(mpg, aes(displ, hwy)) + geom_point() + theme_civilytics()
+  result <- suppressWarnings(p |> civilytics_logo())
+  expect_s3_class(result, "grob")
+})
+
+test_that("civilytics_logo accepts type and variant params", {
+  p <- ggplot(mpg, aes(displ, hwy)) + geom_point() + theme_civilytics_dark()
+  result <- suppressWarnings(civilytics_logo(p, type = "mark", variant = "dark"))
+  expect_s3_class(result, "grob")
 })