feat(operations): fresh platform-operations implementation

Full rewrite of the installer (incl. the finish step), self-update pipeline,
settings store, cron webhook, dashboard/bootstrap surface, environment
manager, wizard login, config endpoint and shared helpers. Byte-compatible
public interfaces and observable behavior, including documented legacy
quirks; verified by the pilot behavioral suite and the full test suite.

app/Platform/Operations/Http/Company/ConfigController.php

@@ -0,0 +1,50 @@
+<?php
+
+namespace App\Platform\Operations\Http\Company;
+
+use App\Platform\Http\Controller;
+use Illuminate\Http\JsonResponse;
+use Illuminate\Http\Request;
+use InvoiceShelf\Modules\Registry;
+
+class ConfigController extends Controller
+{
+    /**
+     * Hand the SPA one value out of the application configuration.
+     *
+     * Exchange-rate drivers are assembled at runtime rather than read from a
+     * config file, so that key takes its own path.
+     */
+    public function __invoke(Request $request): JsonResponse
+    {
+        $key = $request->key;
+
+        if ($key === 'exchange_rate_drivers') {
+            return response()->json(['exchange_rate_drivers' => $this->exchangeRateDrivers()]);
+        }
+
+        return response()->json([$key => config('invoiceshelf.'.$key)]);
+    }
+
+    /**
+     * Build the exchange rate driver list from the module Registry.
+     *
+     * Returns enriched objects (with label, website, and config_fields) so the
+     * frontend can render driver-specific configuration forms without hardcoding
+     * any per-driver UI.
+     *
+     * @return array<int, array<string, mixed>>
+     */
+    protected function exchangeRateDrivers(): array
+    {
+        return collect(Registry::allDrivers('exchange_rate'))
+            ->map(fn (array $meta, string $name) => [
+                'value' => $name,
+                'label' => $meta['label'] ?? $name,
+                'website' => $meta['website'] ?? '',
+                'config_fields' => $meta['config_fields'] ?? [],
+            ])
+            ->values()
+            ->all();
+    }
+}