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/README.md

@@ -0,0 +1,68 @@
+# draw.io Cloudron Package
+
+## Description
+
+draw.io (diagrams.net) is a free, open-source, client-side diagramming
+application for creating flowcharts, process diagrams, organizational charts,
+UML, entity-relationship, network diagrams, and more. It runs entirely in the
+browser; diagrams are stored in browser `localStorage` or exported / synced to
+cloud storage providers (Google Drive, OneDrive, GitHub, GitLab, Dropbox).
+
+This package wraps the official `jgraph/drawio` Docker image (Tomcat serving
+`draw.war`).
+
+## Authentication
+
+draw.io has **no built-in user model** — it is a stateless client-side tool.
+This package therefore uses **Cloudron's authentication proxy**
+(`httpAuth.type = proxy` in `CloudronManifest.json`). The Cloudron admin
+restricts which platform users/groups may reach the app; authorized users are
+challenged for their Cloudron credentials before the diagram editor loads.
+
+This is the recommended pattern for utility apps without their own user
+directory.
+
+## Features
+
+- **Diagram Types**: Flowcharts, BPMN, UML, ERD, network, AWS/Azure/GCP
+  architecture, mind maps, org charts, floor plans, Venn, and more
+- **Shape Libraries**: Hundreds of built-in stencils + custom shape import
+- **Export**: PNG, JPEG, SVG, PDF, HTML, VSDX
+- **Cloud Sync**: Google Drive, OneDrive, GitHub, GitLab, Dropbox, Trello
+- **Offline**: Works fully offline; diagrams persist in the browser
+- **Collaboration**: Real-time co-editing via Google Drive / Microsoft Teams
+- **Embed**: Embed diagrams in Confluence, Jira, Notion, web pages
+
+## Configuration
+
+### Ports
+- **8080**: Tomcat HTTP (the only exposed port)
+
+### Environment Variables (optional)
+draw.io runs out-of-the-box with no configuration. These are optional knobs:
+
+| Variable | Purpose |
+|----------|---------|
+| `DRAWIO_BASE_URL` | Base URL for the deployment |
+| `DRAWIO_SELF_CONTAINED` | `1` to run fully self-contained (no external CDNs) |
+| `PLANTUML_URL` | URL of a PlantUML server for UML rendering |
+| `EXPORT_URL` | URL of a draw.io export server (for server-side PDF/PNG) |
+| `DRAWIO_CSP_URL` | Content Security Policy allowlist |
+
+### Storage
+- **None required.** draw.io is stateless. Diagrams live in the browser or in
+  cloud storage. No Cloudron addons are used.
+
+## Usage
+
+1. Install the package on Cloudron.
+2. In the Cloudron access control, grant the desired users/groups access.
+3. Open the app location — you'll be prompted for Cloudron credentials.
+4. Start drawing. Save diagrams to browser, export to file, or connect a cloud
+   storage provider for persistence.
+
+## Upstream
+
+- **Repository**: https://github.com/jgraph/docker-drawio
+- **Image**: `jgraph/drawio:24.7.17`
+- **Website**: https://www.drawio.com