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/Services/Pdf/ImageUtils.php

@@ -0,0 +1,18 @@
+<?php
+
+namespace App\Services\Pdf;
+
+use Illuminate\Support\Facades\File;
+
+class ImageUtils
+{
+    /**
+     * Convert local path to Base64 encoded data source
+     *
+     * @return string
+     */
+    public static function toBase64Src($path)
+    {
+        return sprintf('data:%s;base64,%s', File::mimeType($path), base64_encode(File::get($path)));
+    }
+}