feat: add draw.io Cloudron package (Documentation-Tools)

draw.io (diagrams.net) is a client-side diagramming app. It has no user
model and no server-side state (diagrams live in the browser or cloud
storage), so this is the first package to use the Cloudron
authentication-proxy pattern: httpAuth.type=proxy gates access at the
platform edge — the admin restricts who can reach it and the browser
challenges for Cloudron credentials.

- Wraps the official jgraph/drawio:24.7.17 Tomcat image (pinned, verified)
- No database / no persistent storage; installs curl for the health check
- HTTP port 8080, health check on /
- Validated: docker build + run return HTTP 200, container healthy

Gardening: STATUS/README/JOURNAL updated (8/~57 packaged); new
"official-image wrapper + auth proxy" pattern documented in JOURNAL.

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Package-Workspace/Documentation-Tools/docker-drawio/CHANGELOG.md

@@ -0,0 +1,10 @@
+# Changelog
+
+## 24.7.17 — Initial Cloudron package
+
+- First Cloudron package for draw.io (diagrams.net)
+- Wraps the official `jgraph/drawio:24.7.17` Tomcat image
+- Fronted by the Cloudron authentication proxy (no app-level users; stateless
+  client-side diagramming tool)
+- No database / no persistent storage required
+- HTTP port 8080, health check on `/`