Set the server's public URL from KEEPORG_EXTERNAL_URL

The image passes neither -config nor -url, so a deployment had no way to
set external_url and the server built invite links, device-approval pages
and the OIDC redirect URI on http://localhost:8765. The variable overrides
the configuration file and -url overrides it. The deployment values set it
to https://keeporg.tiredsysadmin.cc.

Also document every environment variable the server reads, and the
standard proxy and CA variables it honours for OIDC.

Server version 0.8.0.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

config/variables/server.values.yaml

@@ -3,6 +3,8 @@ namespace: "apps"
 environment:
 - name: "KEEPORG_MASTER_KEY_FILE"
   value: "/etc/keeporg/config.txt"
+- name: "KEEPORG_EXTERNAL_URL"
+  value: "https://keeporg.tiredsysadmin.cc"
 image:
   name: "repo.rcmd.space/keeporg"
   version: "v0.1.0"