refactor: migrate package installation from pak to uvr

bincraft dropped pak in favour of uvr, so the pipelines, helper scripts
and images in this repo move with it.

- add local/uvr-install.sh as the single replacement for pak::pak(); it
  bootstraps a pinned uvr, mints a throwaway project under TMPDIR and
  runs `uvr add --no-install` + `uvr sync --library`, because `uvr add`
  refuses to run outside a project and only `sync` honours --library
- install bincraft via its Forgejo spec (forgejo::codefloe.com/rpkgs/
  bincraft@<tag>) instead of a git:: URL, keeping the git ls-remote tag
  resolution
- pass UVR_R_BIN/UVR_TARGET_LIB from install-bincraft.R so the
  per-R-minor passes target their own R and library
- replace R_PKG_CACHE_DIR with UVR_CACHE_DIR/UVR_PACKAGES_DIR on the
  persistent volume, preserving the amd64-off/arm64-on split
- drop trim_pkgcache_metadata() and its test; uvr's cache does not grow
  the way pkgcache's _metadata dir did
- let uvr install system requirements from its vendored
  r-system-requirements rules, replacing pak::sysreqs_db_update()
- migrate the shiny app image, the alpine reprex and the CRAN loading
  test; ship uvr-install.sh in the build-one image
- track the uvr pin with renovate

docker/Containerfile-shiny-app

@@ -1,7 +1,15 @@
 FROM devxygmbh/r-alpine:4.4-3.20 AS build
 
 # ARG GITHUB_PAT
-RUN R -q -e 'install.packages("pak", repos = sprintf("https://r-lib.github.io/p/pak/stable/%s/%s/%s", .Platform$pkgType, R.Version()$os, R.Version()$arch))'
+RUN apk add --no-cache curl ca-certificates \
+  && curl -fsSL https://raw.githubusercontent.com/nbafrank/uvr/main/install.sh \
+    | UVR_INSTALL_DIR=/usr/local/bin sh
+
+# One uvr project drives both dependency installs below. UVR_LIBRARY points the
+# syncs at the image's R library instead of the project-local .uvr/library/, so
+# `Rscript app.R` finds the packages without a uvr-aware .Rprofile.
+ENV UVR_LIBRARY=/usr/lib/R/library
+RUN mkdir -p /uvr && cd /uvr && uvr init --here
 
 COPY --link ./DESCRIPTION .
 COPY --link ./R ./R
@@ -11,13 +19,19 @@ COPY --link ./shiny/app.R /app/app.R
 
 RUN ls -la
 
-# install R package deps
-RUN R -q -e 'pak::pak()'
+# install R package deps. uvr has no equivalent of bare `pak::pak()`, which
+# reads the DESCRIPTION in the working directory, so extract the dependency
+# names and hand them to `uvr add`.
+RUN R -q --no-echo -e "d <- read.dcf('DESCRIPTION'); f <- intersect(colnames(d), c('Depends', 'Imports', 'LinkingTo')); p <- trimws(sub('[(].*', '', unlist(strsplit(paste(d[, f], collapse = ','), ',')))); writeLines(setdiff(p[nzchar(p)], c('R', rownames(installed.packages()))), '/tmp/deps.txt')" \
+  && cd /uvr && xargs -r uvr add --no-install < /tmp/deps.txt \
+  && uvr sync --install-system-deps
 
 RUN R CMD INSTALL --no-docs --without-keep.source  .
 
 # install shiny app deps
-RUN R -q -e "install.packages('renv'); pkgs <- renv::dependencies('/app/app.R')[['Package']]; pkgs = setdiff(pkgs, 'bincraft'); pak::pak(pkgs)"
+RUN R -q -e "install.packages('renv'); pkgs <- renv::dependencies('/app/app.R')[['Package']]; pkgs = setdiff(pkgs, 'bincraft'); writeLines(pkgs, '/tmp/app-deps.txt')" \
+  && cd /uvr && xargs -r uvr add --no-install < /tmp/app-deps.txt \
+  && uvr sync --install-system-deps
 
 ENV PGPASS=""