feat(knowledge-base): Knowledge Base UI — browse/edit, modal, project links

- Knowledge Bases list page + sidebar entry + "+ New" create modal
- Detail page with a recursive structure tree: add/edit/delete topics,
  categories and facts inline, including name + description editing
- Create/metadata-edit modal (title, description)
- Project edit modal gains a link/remove knowledge base section
- Types and routes for /knowledge-bases and /knowledge-bases/:id
- Scoped .kb-* styles (contained panel, topic cards, hierarchy guides)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/components/Sidebar.tsx

@@ -35,6 +35,7 @@ export default function Sidebar({ user, onLogout }: Props) {
   const links = user ? [
     { to: '/', icon: '📊', label: 'Dashboard' },
     { to: '/projects', icon: '📁', label: 'Projects' },
+    { to: '/knowledge-bases', icon: '📚', label: 'Knowledge Bases' },
     { to: '/proposals', icon: '💡', label: 'Proposals' },
     { to: '/calendar', icon: '📅', label: 'Calendar' },
     { to: '/notifications', icon: '🔔', label: 'Notifications' + (unreadCount > 0 ? ' (' + unreadCount + ')' : '') },