Replace custom setup wizard with Database Manager (like Python Odoo)

Flow now mirrors Python Odoo exactly:
1. Empty DB → /web redirects to /web/database/manager
2. User fills: master_pwd, email (login), password, phone, lang, country, demo
3. Backend creates admin user, company, seeds chart of accounts
4. Auto-login → redirect to /odoo (webclient)

Removed:
- Custom /web/setup wizard
- Auto-seed on startup

Added:
- /web/database/manager (mirrors odoo/addons/web/controllers/database.py)
- /web/database/create (mirrors exp_create_database)
- Auto-login after DB creation with session cookie

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pkg/server/server.go

@@ -95,9 +95,9 @@ func (s *Server) registerRoutes() {
 	// Database endpoints
 	s.mux.HandleFunc("/web/database/list", s.handleDBList)
 
-	// Setup wizard
-	s.mux.HandleFunc("/web/setup", s.handleSetup)
-	s.mux.HandleFunc("/web/setup/install", s.handleSetupInstall)
+	// Database manager (mirrors Python Odoo's /web/database/manager)
+	s.mux.HandleFunc("/web/database/manager", s.handleDatabaseManager)
+	s.mux.HandleFunc("/web/database/create", s.handleDatabaseCreate)
 
 	// Image serving (placeholder for uploaded images)
 	s.mux.HandleFunc("/web/image", s.handleImage)