feat: team-based visibility, roles management, unified users, UI fixes

- Add Roles table with CRUD routes and Settings page management
- Unify user management: remove Users page, enhance Team page with
  permission level + role dropdowns
- Add team-based visibility scoping to projects, campaigns, posts,
  tasks, issues, artefacts, and dashboard
- Add team_id to projects and campaigns (create + edit forms)
- Add getUserTeamIds/getUserVisibilityContext helpers
- Fix Budgets modal horizontal scroll (separate linked-to row)
- Add collapsible filter bar to PostProduction page

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

client/src/components/Sidebar.jsx

@@ -3,7 +3,7 @@ import { NavLink } from 'react-router-dom'
 import {
   LayoutDashboard, FileEdit, Image, Calendar, Wallet,
   FolderKanban, CheckSquare, Users, ChevronLeft, ChevronRight, ChevronDown,
-  Sparkles, Shield, LogOut, User, Settings, Languages, Tag, LayoutList, Receipt, BarChart3, Palette, CalendarDays, AlertCircle
+  Sparkles, LogOut, User, Settings, Languages, Tag, LayoutList, Receipt, BarChart3, Palette, CalendarDays, AlertCircle
 } from 'lucide-react'
 import { useAuth } from '../contexts/AuthContext'
 import { useLanguage } from '../i18n/LanguageContext'
@@ -167,23 +167,6 @@ export default function Sidebar({ collapsed, setCollapsed }) {
           {standaloneBottom.map(item => navLink(item))}
         </div>
 
-        {/* Superadmin Only: Users Management */}
-        {currentUser?.role === 'superadmin' && (
-          <NavLink
-            to="/users"
-            className={({ isActive }) =>
-              `flex items-center gap-3 px-3 py-2 rounded-lg text-sm font-medium transition-all duration-200 group ${
-                isActive
-                  ? 'bg-white/15 text-white shadow-sm'
-                  : 'text-text-on-dark-muted hover:bg-white/8 hover:text-white'
-              }`
-            }
-          >
-            <Shield className="w-5 h-5 shrink-0" />
-            {!collapsed && <span className="animate-fade-in whitespace-nowrap">{t('nav.users')}</span>}
-          </NavLink>
-        )}
-
         {/* Settings (visible to all) */}
         <NavLink
           to="/settings"