Jenkins Build image with Plugin

Hi Experts,

I am building a Jenkins image with recommended plugins. The build flow is like, download the latest lts-jdk21 image, update our own certs, download and install plugins. The download + certs install works fine. But while downloading, the URL is not working.

```
STEP 14/14: RUN jenkins-plugin-cli -f /usr/share/jenkins/ref/plugins.txt && mkdir -p $JENKINS_HOME && chown -R jenkins:jenkins $JENKINS_HOME
Jun 30, 2025 3:07:06 PM org.apache.http.impl.execchain.RetryExec execute
INFO: I/O exception (org.apache.http.NoHttpResponseException) caught when processing request to {s}->https://eastamerica.cloudflare.jenkins.io:443: The target server failed to respond
Jun 30, 2025 3:07:06 PM org.apache.http.impl.execchain.RetryExec execute
INFO: Retrying request to {s}->https://eastamerica.cloudflare.jenkins.io:443
Jun 30, 2025 3:07:06 PM org.apache.http.impl.execchain.RetryExec execute
INFO: I/O exception (org.apache.http.NoHttpResponseException) caught when processing request to {s}->https://eastamerica.cloudflare.jenkins.io:443: The target server failed to respond
Jun 30, 2025 3:07:06 PM org.apache.http.impl.execchain.RetryExec execute
INFO: Retrying request to {s}->https://eastamerica.cloudflare.jenkins.io:443
Jun 30, 2025 3:07:06 PM org.apache.http.impl.execchain.RetryExec execute
INFO: I/O exception (org.apache.http.NoHttpResponseException) caught when processing request to {s}->https://eastamerica.cloudflare.jenkins.io:443: The target server failed to respond
Jun 30, 2025 3:07:06 PM org.apache.http.impl.execchain.RetryExec execute
INFO: Retrying request to {s}->https://eastamerica.cloudflare.jenkins.io:443
Unable to retrieve JSON from https://updates.jenkins.io/update-center.json?version=2.504.3: eastamerica.cloudflare.jenkins.io:443 failed to respond
Tried downloading update-center-2.504.3 from https://eastamerica.cloudflare.jenkins.io/dynamic-stable-2.504.2/update-center.json (attempt 1 of 3)
Jun 30, 2025 3:07:07 PM org.apache.http.impl.execchain.RetryExec execute
INFO: I/O exception (org.apache.http.NoHttpResponseException) caught when processing request to {s}->https://eastamerica.cloudflare.jenkins.io:443: The target server failed to respond
Jun 30, 2025 3:07:07 PM org.apache.http.impl.execchain.RetryExec execute
INFO: Retrying request to {s}->https://eastamerica.cloudflare.jenkins.io:443
Jun 30, 2025 3:07:07 PM org.apache.http.impl.execchain.RetryExec execute
INFO: I/O exception (org.apache.http.NoHttpResponseException) caught when processing request to {s}->https://eastamerica.cloudflare.jenkins.io:443: The target server failed to respond
Jun 30, 2025 3:07:07 PM org.apache.http.impl.execchain.RetryExec execute
INFO: Retrying request to {s}->https://eastamerica.cloudflare.jenkins.io:443
Jun 30, 2025 3:07:07 PM org.apache.http.impl.execchain.RetryExec execute
INFO: I/O exception (org.apache.http.NoHttpResponseException) caught when processing request to {s}->https://eastamerica.cloudflare.jenkins.io:443: The target server failed to respond
Jun 30, 2025 3:07:07 PM org.apache.http.impl.execchain.RetryExec execute
INFO: Retrying request to {s}->https://eastamerica.cloudflare.jenkins.io:443
Unable to retrieve JSON from https://updates.jenkins.io/update-center.json?version=2.504.3: eastamerica.cloudflare.jenkins.io:443 failed to respond
Tried downloading update-center-2.504.3 from https://eastamerica.cloudflare.jenkins.io/dynamic-stable-2.504.2/update-center.json (attempt 2 of 3)
Jun 30, 2025 3:07:08 PM org.apache.http.impl.execchain.RetryExec execute
INFO: I/O exception (org.apache.http.NoHttpResponseException) caught when processing request to {s}->https://eastamerica.cloudflare.jenkins.io:443: The target server failed to respond
Jun 30, 2025 3:07:08 PM org.apache.http.impl.execchain.RetryExec execute
INFO: Retrying request to {s}->https://eastamerica.cloudflare.jenkins.io:443
Jun 30, 2025 3:07:08 PM org.apache.http.impl.execchain.RetryExec execute
INFO: I/O exception (org.apache.http.NoHttpResponseException) caught when processing request to {s}->https://eastamerica.cloudflare.jenkins.io:443: The target server failed to respond
Jun 30, 2025 3:07:08 PM org.apache.http.impl.execchain.RetryExec execute
INFO: Retrying request to {s}->https://eastamerica.cloudflare.jenkins.io:443
Jun 30, 2025 3:07:08 PM org.apache.http.impl.execchain.RetryExec execute
INFO: I/O exception (org.apache.http.NoHttpResponseException) caught when processing request to {s}->https://eastamerica.cloudflare.jenkins.io:443: The target server failed to respond
Jun 30, 2025 3:07:08 PM org.apache.http.impl.execchain.RetryExec execute
INFO: Retrying request to {s}->https://eastamerica.cloudflare.jenkins.io:443
Tried downloading update-center-2.504.3 from https://eastamerica.cloudflare.jenkins.io/dynamic-stable-2.504.2/update-center.json (attempt 3 of 3)
Error getting update center json
Error: building at STEP "RUN jenkins-plugin-cli -f /usr/share/jenkins/ref/plugins.txt && mkdir -p $JENKINS_HOME && chown -R jenkins:jenkins $JENKINS_HOME": while running runtime: exit status 1
```

Start with the image build's `RUN jenkins-plugin-cli -f /usr/share/jenkins/ref/plugins.txt` step and the referenced `/usr/share/jenkins/ref/plugins.txt`; inspect the update-center requests to `updates.jenkins.io` and `eastamerica.cloudflare.jenkins.io`. Done means reproducing the failure and establishing a verified resolution for retrieving the update-center JSON and installing the listed plugins.

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