fix(security): gate AI tools by user ability and block admin-URL SSRF

The AI chat assistant scoped tool queries by company but ignored the
per-user Bouncer abilities the rest of the app enforces, so any `use ai`
holder could read customers, invoices, payments, and company financials
their role couldn't otherwise see. Each AiTool now declares a required
ability (entity-aligned); the registry hides unauthorized tools from the
model and refuses to execute them as a backstop.

Separately, admin/owner-supplied URLs were fetched server-side with no
guard against private/reserved targets (SSRF): the AI base URL, the
CurrencyConverter "DEDICATED" exchange-rate URL, and S3/Spaces file-disk
endpoints. A shared PrivateNetworkGuard now backs a PublicHttpUrl
validation rule (save-time) and runtime guards in each driver.

- AiTool::requiredAbility() + mapping across all 12 tools
- AiToolRegistry filters schemas() by ability and re-checks in execute()
- PrivateNetworkGuard / BlockedUrlException / PublicHttpUrl rule (new)
- Rule wired into AI config (service + 3 controllers), exchange-rate,
  and file-disk endpoints; runtime guards in OpenRouterDriver,
  CurrencyConverterDriver, and FileDiskService
- Tests for ability filtering, the guard, the rule, and 422 rejections

app/Http/Requests/ExchangeRateProviderRequest.php

@@ -2,6 +2,7 @@
 
 namespace App\Http\Requests;
 
+use App\Rules\PublicHttpUrl;
 use Illuminate\Foundation\Http\FormRequest;
 
 class ExchangeRateProviderRequest extends FormRequest
@@ -35,6 +36,14 @@ class ExchangeRateProviderRequest extends FormRequest
             'driver_config' => [
                 'nullable',
             ],
+            // Only the CurrencyConverter "DEDICATED" plan reads a custom URL from
+            // driver_config; guard it against SSRF (private/reserved targets).
+            'driver_config.url' => [
+                'nullable',
+                'string',
+                'url',
+                new PublicHttpUrl,
+            ],
             'active' => [
                 'nullable',
                 'boolean',