Phase 1 MVP - Complete implementation

- Login with JWT and refresh token rotation
- Dashboard with projects cards
- ProjectView with TreeView navigation
- DocumentView with markdown editor and auto-save
- Tag management (create, assign, remove)
- Dark mode CSS variables
- Security fixes applied (logout to backend, createDocument endpoint)

node_modules/postcss/lib/stringify.js

@@ -0,0 +1,11 @@
+'use strict'
+
+let Stringifier = require('./stringifier')
+
+function stringify(node, builder) {
+  let str = new Stringifier(builder)
+  str.stringify(node)
+}
+
+module.exports = stringify
+stringify.default = stringify