chore: establish M0 project foundations

Document accepted MVP decisions, add AGPL-3.0-only licensing, scaffold repository boundaries, and configure verified PSR-12 and foundation checks.

Refs #1, #2, #3, #4, #5

docker/README.md

@@ -0,0 +1,7 @@
+# Container configuration
+
+M1 issue #6 adds nginx, PHP-FPM, PostgreSQL and asset build services. There is no
+Compose file yet. Keep database data, managed library files and uploaded media
+persistent and outside the application source. Mount import sources read-only
+where possible. Node is asset tooling in MVP, not a required mesh-processing
+runtime. Never bake credentials or user collections into images.