feat: bump title sizes, add font_scale to logo functions, ship SVGs

- Change rel_large default from 16/14 to 20/14 (~1.43x) to match the
  Civilytics editorial design system. Subtitle now renders at 1.0x base
  instead of 0.86x.
- Switch axis.text to rel() sizing so all text elements cascade from the
  root font_size, enabling uniform scaling.
- Add font_scale parameter (default 1.1) to civilytics_logo(),
  add_logo(), and add_logo_ga() — inflates text by ~10% before
  arrangeGrob composition to compensate for viewport shrinkage.
- Ship SVG logo variants (mark, wordmark, pulse) in inst/img/ for
  Quarto/HTML templates.
- Add "Maintaining brand assets" section to README documenting inst/img/
  file inventory and update workflow.
- Document full font size hierarchy in theme_civilytics() roxygen.

man/civilytics_logo.Rd

@@ -8,7 +8,8 @@ civilytics_logo(
   plot,
   type = c("wordmark", "mark"),
   variant = c("light", "dark"),
-  margin_param = NULL
+  margin_param = NULL,
+  font_scale = 1.1
 )
 }
 \arguments{
@@ -22,6 +23,10 @@ civilytics_logo(
 
 \item{margin_param}{Numeric or `NULL`. Manual margin adjustment passed to
 [add_logo()].}
+
+\item{font_scale}{Numeric. Inflate text sizes by this factor to compensate
+for viewport shrinkage when composing with [gridExtra::arrangeGrob()].
+Default `1.1` (~10 \% inflation). Set to `1` to disable.}
 }
 \value{
 A grob (from [gridExtra::arrangeGrob()]) ready to draw with
@@ -59,5 +64,12 @@ library(ggplot2); library(grid)
   theme_civilytics_dark()) |>
   civilytics_logo(variant = "dark", type = "mark") |>
   grid.draw()
+
+# Disable font inflation
+(ggplot(mpg, aes(displ, hwy)) +
+  geom_point() +
+  theme_civilytics()) |>
+  civilytics_logo(font_scale = 1) |>
+  grid.draw()
 }
 }