fix: navigation correctness - back buttons, exit dialog, dedup nav, redirects

- Standardize all procedural back/exit paths to /trees (not /my-trees)
- Add exit button with ConfirmDialog to procedural session top bar
- Consolidate duplicate account links in sidebar and topbar
- Auto-redirect non-owners to personal analytics
- Add toast feedback before silent permission redirects in tree editor
- Delete orphaned AdminCategoriesPage

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/components/layout/Sidebar.tsx

@@ -1,6 +1,6 @@
 import { useEffect, useState } from 'react'
 import { useNavigate, useLocation } from 'react-router-dom'
-import { LayoutGrid, Box, PenLine, Clock, FileText, Bookmark, BarChart3, Users, Settings, PanelLeftClose, PanelLeftOpen, MessageSquareText } from 'lucide-react'
+import { LayoutGrid, Box, PenLine, Clock, FileText, Bookmark, BarChart3, Settings, PanelLeftClose, PanelLeftOpen, MessageSquareText } from 'lucide-react'
 import { cn } from '@/lib/utils'
 import { useUserPreferencesStore } from '@/store/userPreferencesStore'
 import { CategoryList } from '@/components/sidebar/CategoryList'
@@ -203,8 +203,7 @@ export function Sidebar() {
         {!sidebarCollapsed && (
           <>
             <NavItem href="/feedback" icon={MessageSquareText} label="Feedback" />
-            <NavItem href="/account" icon={Users} label="Team" />
-            <NavItem href="/account" icon={Settings} label="Settings" />
+            <NavItem href="/account" icon={Settings} label="Account" />
           </>
         )}
         <button