Remove app/Space folder and extract model business logic into services

Relocate all 14 files from the catch-all app/Space namespace into proper
locations: data providers to Support/Formatters, installation utilities to
Services/Installation, PDF utils to Services/Pdf, module/update classes to
Services/Module and Services/Update, SiteApi trait to Traits, and helpers
to Support.

Extract ~1,400 lines of business logic from 8 fat models (Invoice, Payment,
Estimate, RecurringInvoice, Company, Customer, Expense, User) into 9 new
service classes with constructor injection. Controllers now depend on
services instead of calling static model methods. Shared item/tax creation
logic consolidated into DocumentItemService.

app/Http/Controllers/V1/PDF/InvoicePdfController.php

@@ -4,11 +4,16 @@ namespace App\Http\Controllers\V1\PDF;
 
 use App\Http\Controllers\Controller;
 use App\Models\Invoice;
+use App\Services\InvoiceService;
 use Illuminate\Http\Request;
 use Illuminate\Http\Response;
 
 class InvoicePdfController extends Controller
 {
+    public function __construct(
+        private readonly InvoiceService $invoiceService,
+    ) {}
+
     /**
      * Handle the incoming request.
      *
@@ -17,7 +22,7 @@ class InvoicePdfController extends Controller
     public function __invoke(Request $request, Invoice $invoice)
     {
         if ($request->has('preview')) {
-            return $invoice->getPDFData();
+            return $this->invoiceService->getPdfData($invoice);
         }
 
         return $invoice->getGeneratedPDFOrStream('invoice');