Add CERT_PROFILE support and simplify renewal scheduling

Add CERT_PROFILE env var for Let's Encrypt cert profiles. Run certbot
twice daily via a cron entry with a random delay instead of the previous
sed-based cron randomization. Update changelog.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

readme-vars.yml

@@ -32,6 +32,7 @@ opt_param_usage_include_env: true
 opt_param_env_vars:
   - {env_var: "SUBDOMAINS", env_value: "www,", desc: "Subdomains you'd like the cert to cover (comma separated, no spaces) ie. `www,ftp,cloud`. For a wildcard cert, set this *exactly* to `wildcard` (wildcard cert is available via `dns` validation only)"}
   - {env_var: "CERTPROVIDER", env_value: "", desc: "Optionally define the cert provider. Set to `zerossl` for ZeroSSL certs (requires existing [ZeroSSL account](https://app.zerossl.com/signup) and the e-mail address entered in `EMAIL` env var). Otherwise defaults to Let's Encrypt."}
+  - {env_var: "CERT_PROFILE", env_value: "", desc: "Optionally define a cert profile to use for cert generation. This is useful if you want to use a custom cert profile instead of the default one. Currently only supported for Let's Encrypt. See https://letsencrypt.org/docs/profiles/ "}
   - {env_var: "DNSPLUGIN", env_value: "cloudflare", desc: "Required if `VALIDATION` is set to `dns`. Options are `acmedns`, `aliyun`, `azure`, `bunny`, `cloudflare`, `cpanel`, `desec`, `digitalocean`, `directadmin`, `dnsimple`, `dnsmadeeasy`, `dnspod`, `do`, `domeneshop`, `dreamhost`, `duckdns`, `dynu`, `freedns`, `gandi`, `gehirn`, `glesys`, `godaddy`, `google`, `he`, `hetzner`, `hetzner-cloud`, `infomaniak`, `inwx`, `ionos`, `linode`, `loopia`, `luadns`, `mijn-host`, `namecheap`, `netcup`, `njalla`, `nsone`, `ovh`, `porkbun`, `rfc2136`, `route53`, `sakuracloud`, `standalone`, `transip`, and `vultr`. Also need to enter the credentials into the corresponding ini (or json for some plugins) file under `/config/dns-conf`."}
   - {env_var: "PROPAGATION", env_value: "", desc: "Optionally override (in seconds) the default propagation time for the dns plugins."}
   - {env_var: "EMAIL", env_value: "", desc: "Optional e-mail address used for cert expiration notifications (Required for ZeroSSL)."}
@@ -65,7 +66,7 @@ app_setup_block: |
       2. Certs that cover sub-subdomains of your main subdomain (ie. `*.yoursubdomain.duckdns.org`, set the `SUBDOMAINS` variable to `wildcard`)
   * `--cap-add=NET_ADMIN` is required for fail2ban to modify iptables
   * After setup, navigate to `https://example.com` to access the default homepage (http access through port 80 is disabled by default, you can enable it by editing the default site config at `/config/nginx/site-confs/default.conf`).
-  * Certs are checked nightly and if expiration is within 30 days, renewal is attempted. If your cert is about to expire in less than 30 days, check the logs under `/config/log/letsencrypt` to see why the renewals have been failing. It is recommended to input your e-mail in docker parameters so you receive expiration notices from Let's Encrypt in those circumstances.
+  * Certs are checked twice daily using ACME Renewal Information (ARI) to determine the optimal renewal window. If your cert is about to expire, check the logs under `/config/log/letsencrypt` to see why the renewals have been failing.
 
   ### Certbot Plugins
 
@@ -219,6 +220,7 @@ init_diagram: |
   "swag:latest" <- Base Images
 # changelog
 changelogs:
+  - {date: "10.07.26:", desc: "Add support for Let's Encrypt cert profiles. Run certbot twice daily with a random delay." }
   - {date: "19.06.26:", desc: "Add support for mijn.host dns validation."}
   - {date: "01.06.26:", desc: "Remove obsolete old cert check logic."}
   - {date: "23.01.26:", desc: "Reorder init to fix proxy conf version checks."}