chore: clean up repo for public release

- Remove BMAD framework, IDE configs, dev screenshots, test files,
  internal docs, and backup files
- Rename keep-notes/ to memento-note/
- Update all references from keep-notes to memento-note
- Add Apache 2.0 license with Commons Clause (non-commercial restriction)
- Add clean .gitignore and .env.docker.example

memento-note/public/icons/icon-192.svg

@@ -0,0 +1,4 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 192 192">
+  <rect width="192" height="192" fill="#f59e0b" rx="40"/>
+  <path d="M50 50 h92 v92 h-92 z" fill="#fff"/>
+</svg>

memento-note/public/icons/icon-512.svg

@@ -0,0 +1,5 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 512 512">
+  <rect width="512" height="512" fill="#f59e0b" rx="100"/>
+  <path d="M150 150 h212 v212 h-212 z" fill="#fff"/>
+  <path d="M150 150 h212" stroke="#fff3cd" stroke-width="20"/>
+</svg>