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/symbols.js

@@ -0,0 +1,5 @@
+'use strict'
+
+module.exports.isClean = Symbol('isClean')
+
+module.exports.my = Symbol('my')