ci: replace Jenkins with Gitea Actions, modernize DESCRIPTION

- Add real R CMD check workflow via Gitea Actions (rocker/r-ver:4.4)
- Remove Jenkinsfile and demo workflow
- Modernize DESCRIPTION: Authors@R, R >= 4.1.0, URL/BugReports fields,
  move tidycensus from Imports to Suggests, testthat edition 3
- Fix agresti_coull_interval: correct implementation, export it
- Convert get_fips/get_stabbr to use requireNamespace for tidycensus
- Remove civilytics:: self-reference in rnh()

NAMESPACE

@@ -1,5 +1,6 @@
 # Generated by roxygen2: do not edit by hand
 
+export(agresti_coull_interval)
 export(add_logo)
 export(add_logo_ga)
 export(clopper_pearson)
@@ -39,7 +40,6 @@ export(waldInterval)
 export(z_gap_test)
 export(z_univariate)
 import(ggplot2)
-import(tidycensus)
 importFrom(ggplot2,theme)
 importFrom(graphics,plot)
 importFrom(graphics,rasterImage)