fix(ci): actually purge BunnyCDN cache in purge_cdn_cache.sh (#78)

## Summary

While cleaning this up I noticed the script **defined** `purge_cdn_cache()` but never **called** it. Every CI run only declared the helper and exited cleanly without issuing a single curl. The PACKAGES freshness on cran.devxy.io / cran.rpkgs.com has been carried entirely by R's `Cache-Control: no-cache` header on the index files.

Fixes in one shot:

1. **Actually run the purge.** The shifted args (`api_key`, `arch`, `os_id`, `domain…`) are now consumed inline and a curl POST is issued per (domain × resource).
2. **Drop `set -x`** — leaked the `AccessKey:` header into job logs.
3. **Drop the Python URL-encoder.** `curl -G --data-urlencode "url=…" --data "async=false" https://api.bunny.net/purge` does the same with no Python. The workflow purge steps can later switch from `alpine:3.23 + apk add bash curl` to a slimmer curl-only image.
4. **Add `src/contrib/Meta/archive.rds`** to the purged resource list. It's rewritten on every `process_cran_updates` run (see README) and was being served stale.

## Risks

- This is the **first time** the script actually purges anything. If anything else (e.g. a downstream service) relied on the no-op behavior, this PR is the moment it stops being silent. I don't see any such caller.
- Edge cache miss right after a purge means an origin S3 fetch — minor latency uptick on the first request per region per resource.

Reviewed-on: #78

scripts/purge_cdn_cache.sh

@@ -1,64 +1,44 @@
-#!/bin/bash
+#!/usr/bin/env bash
+#
+# Purge BunnyCDN edge cache for the index files of one ARCH+OS_ID
+# combination across one or more domains.
+#
+# Usage:
+#   purge_cdn_cache.sh <BUNNYNET_API_KEY> <ARCH> <OS_ID> <domain> [<domain>...]
+#
+set -euo pipefail
 
-set -o pipefail
-set -x
+if (( $# < 4 )); then
+  echo "usage: $0 <api_key> <arch> <os_id> <domain> [<domain>...]" >&2
+  exit 2
+fi
 
-# Function to URL-encode a string using Python
-urlencode() {
-  python3 -c "import urllib.parse, sys; print(urllib.parse.quote(sys.argv[1], safe=''))" "$1"
+api_key="$1"
+arch="$2"
+os_id="$3"
+shift 3
+
+resources=(
+  "src/contrib/PACKAGES"
+  "src/contrib/PACKAGES.gz"
+  "src/contrib/PACKAGES.rds"
+  "src/contrib/PACKAGES.db"
+  "src/contrib/Meta/archive.rds"
+)
+
+purge_one() {
+  local target="$1"
+  # --data-urlencode encodes value of `url=` for us; -G forces GET.
+  curl -sS -G -X POST \
+    -H "AccessKey: ${api_key}" \
+    --data-urlencode "url=${target}" \
+    --data "async=false" \
+    "https://api.bunny.net/purge"
+  echo
 }
 
-# Function to send the purge request using the provided API key
-purge() {
-  local api_key="$1"
-  local url="$2"
-  curl -vL -X POST -H "AccessKey: $api_key" "$url"
-}
-
-# Function to generate the purge URLs for a given domain, arch, and OS ID
-generate_urls() {
-  local domain="$1"
-  local arch="$2"
-  local os_id="$3"
-
-  # Array of resource paths (can be modified or extended as needed)
-  local resources=(
-    "src/contrib/PACKAGES"
-    "src/contrib/PACKAGES.gz"
-    "src/contrib/PACKAGES.rds"
-    "src/contrib/PACKAGES.db"
-  )
-
-  local urls=()
+for domain in "$@"; do
   for resource in "${resources[@]}"; do
-    local target_url="https://${domain}/${arch}/${os_id}/latest/${resource}"
-    local encoded
-    encoded=$(urlencode "$target_url")
-    urls+=( "https://api.bunny.net/purge?url=${encoded}&async=false" )
+    purge_one "https://${domain}/${arch}/${os_id}/latest/${resource}"
   done
-
-  echo "${urls[@]}"
-}
-
-# Function to process multiple domains.
-# Usage: process_domains <BUNNYNET_API_KEY> <ARCH> <OS_ID> domain1 [domain2 ... domainN]
-purge_cdn_cache() {
-  local api_key="$1"
-  local arch="$2"
-  local os_id="$3"
-  shift 3  # Remove the first three arguments, leaving the domains
-
-  for domain in "$@"; do
-    # Generate the list of URLs for the current domain
-    local urls
-    urls=($(generate_urls "$domain" "$arch" "$os_id"))
-
-    # Purge each URL
-    for url in "${urls[@]}"; do
-      purge "$api_key" "$url"
-    done
-  done
-}
-
-# Example usage:
-# purge_cdn_cache "$BUNNYNET_API_KEY" "$ARCH" "$OS_ID" "domain1.com" "domain2.com"
+done