chore: Add CocoaPod keepalive job (#7142)

Creates a daily job that uses cocoapods token so its expiration time
increases.

## Motivation

Cocoapods tokens now expire 3 days after being last used, but we don't
want to update them manually every time we make a release.

---------

Co-authored-by: Burak Yigit Kaya <byk@sentry.io>

Author: itaybre

.github/workflows/cocoapods-keepalive.yml

@@ -0,0 +1,28 @@
+name: "CocoaPods Token Keep-Alive"
+
+on:
+  schedule:
+    # CocoaPods sessions currently expire after 3 days of inactivity (VALIDITY_LENGTH)
+    # This runs every day at midnight UTC to keep the current token alive
+    # See: https://github.com/CocoaPods/trunk.cocoapods.org/blob/a1869790e9ae2229b6985b6af4532da814202558/app/models/session.rb#L9
+    - cron: "0 0 * * *" # Runs every day at midnight UTC
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  keepalive:
+    name: Refresh CocoaPods Session
+    runs-on: macos-15
+    environment: production
+    env:
+      COCOAPODS_TRUNK_TOKEN: ${{ secrets.COCOAPODS_TRUNK_TOKEN }}
+
+    steps:
+      - name: Install CocoaPods
+        run: gem install cocoapods
+      - name: Print CocoaPods Version
+        run: pod --version
+      - name: Refresh CocoaPods Session
+        run: pod trunk me > /dev/null 2>&1