feat: initialize Grav multi-site project

- Add AGENTS.md with project requirements and site inventory
- Add JOURNAL.md for project tracking
- Add etc-hosts-entries.txt for local testing (22 domains)
- Add setup.php for Grav multi-site routing configuration

This project migrates 21 mdbook sites to a single Grav multi-site
installation. Each site will have its own environment directory under
user/env/{fqdn}/ with independent config, pages, and themes.

Development runs in Docker on port 12000 (container: tsysstatic-dev-grav).
Production target: Cloudron Grav app at staticsites.turnsys.com.

🤖 Generated with [Crush](https://crush.cbhops.com)

Assisted-by: GLM-5 via Crush <crush@charm.land>

JOURNAL.md

@@ -0,0 +1,23 @@
+# Project Journal
+
+## 2026-03-02
+
+### 15:52 - Project Initiated
+- Explored existing mdbook repositories (21 sites found)
+- Researched Grav multi-site capabilities:
+  - Grav supports environment-based multi-site via `user/env/{hostname}/`
+  - Each site can have independent git repository
+  - Domain routing via setup.php or environment variables
+- Researched Grav Docker setup: `getgrav/grav:latest` image
+
+### 15:53 - Requirements Captured
+- Created AGENTS.md with project requirements
+- Container naming convention: `tsysstatic-dev-*`
+- Development port: 12000
+
+### Next Steps
+- [ ] Start Grav Docker container on port 12000
+- [ ] Create /etc/hosts input file for local testing
+- [ ] Configure Grav multi-site structure
+- [ ] Create per-site environment directories
+- [ ] Initialize git repository