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()

.gitea/workflows/check.yaml

@@ -0,0 +1,46 @@
+name: R-CMD-check
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: [master]
+
+jobs:
+  check:
+    name: R CMD check
+    runs-on: ubuntu-latest
+    container: rocker/r-ver:4.4
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install system dependencies
+        run: |
+          apt-get update -qq
+          apt-get install -y --no-install-recommends \
+            libcurl4-openssl-dev \
+            libssl-dev \
+            libxml2-dev \
+            libcairo2-dev \
+            libjpeg-dev \
+            libpng-dev \
+            libfontconfig1-dev \
+            libharfbuzz-dev \
+            libfribidi-dev \
+            libfreetype6-dev \
+            libtiff5-dev
+
+      - name: Install R dependencies
+        run: |
+          install.packages(c("remotes", "rcmdcheck"))
+          remotes::install_deps(dependencies = TRUE)
+        shell: Rscript {0}
+
+      - name: Run R CMD check
+        run: rcmdcheck::rcmdcheck(args = "--no-manual", error_on = "warning")
+        shell: Rscript {0}
+
+      - name: Run tests
+        run: testthat::test_local(".", reporter = "progress")
+        shell: Rscript {0}