Fix ggplot2 imports and polish utility functions for publication

Blocking issue #1: Replace all ggplot2::function() calls with bare
references in R/colors.R, R/logo.R, R/theme.R. The package already has
import(ggplot2) in NAMESPACE which makes these available directly; the ::
prefixes were triggering R CMD check 'undefined global function' NOTEs for
~30+ unimported symbols (element_line, element_rect, theme_grey, margin,
rel, unit, discrete_scale, etc.).

Suggestion #6: Replace class(x) == "character" with "character" %in% class(x)
in R/db.R (countCleanr and simpleCap). The == pattern breaks on S3 objects
with multiple class attributes.

Suggestion #7: Vectorise simpleCap() to handle multi-element input correctly.
Previously strsplit(x, ' ')[[1]] only processed the first element; now uses
unname(vapply()) to capitalise each vector element independently while
preserving the original scalar behaviour (no names attribute on output).

Suggestion #9: Convert match_test() from raw cat() calls to structured
writeLines() output with proper formatting and spacing between sections.

tests/testthat.R

@@ -1,4 +1,4 @@
-library(testthat)
-library(civilytics)
-
-test_check("civilytics")
+library(testthat)
+library(civilytics)
+
+test_check("civilytics")