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

phpcs.xml.dist

@@ -0,0 +1,11 @@
+<?xml version="1.0"?>
+<ruleset name="MeshVault">
+    <description>MeshVault PHP coding standard: PSR-12.</description>
+    <rule ref="PSR12"/>
+    <arg name="extensions" value="php"/>
+    <arg name="encoding" value="utf-8"/>
+    <file>src</file>
+    <file>public</file>
+    <file>db/migrations</file>
+    <file>tests</file>
+</ruleset>