Add company invitation system (backend)

New feature allowing company owners/admins to invite users by email with
a specific company-scoped role.

Database:
- New company_invitations table (company_id, email, role_id, token,
  status, invited_by, expires_at)

Backend:
- CompanyInvitation model with pending/forUser scopes
- InvitationService: invite, accept, decline, getPendingForUser
- CompanyInvitationMail with markdown email template
- InvitationController (company-scoped): list, send, cancel invitations
- InvitationResponseController (user-scoped): pending, accept, decline
- BootstrapController returns pending_invitations in response
- CompanyMiddleware handles zero-company users gracefully

Tests: 9 feature tests covering invite, accept, decline, cancel, expire,
duplicate prevention, and bootstrap integration.

app/Http/Controllers/Company/General/BootstrapController.php

@@ -3,9 +3,11 @@
 namespace App\Http\Controllers\Company\General;
 
 use App\Http\Controllers\Controller;
+use App\Http\Resources\CompanyInvitationResource;
 use App\Http\Resources\CompanyResource;
 use App\Http\Resources\UserResource;
 use App\Models\Company;
+use App\Models\CompanyInvitation;
 use App\Models\CompanySetting;
 use App\Models\Currency;
 use App\Models\Module;
@@ -28,13 +30,47 @@ class BootstrapController extends Controller
     {
         $current_user = $request->user();
         $current_user_settings = $current_user->getAllSettings();
+        $companies = $current_user->companies;
+
+        $pendingInvitations = CompanyInvitation::forUser($current_user)
+            ->pending()
+            ->with(['company', 'role', 'invitedBy'])
+            ->get();
+
+        $global_settings = Setting::getSettings([
+            'api_token',
+            'admin_portal_theme',
+            'admin_portal_logo',
+            'login_page_logo',
+            'login_page_heading',
+            'login_page_description',
+            'admin_page_title',
+            'copyright_text',
+            'save_pdf_to_disk',
+        ]);
+
+        // User has no companies — return minimal bootstrap
+        if ($companies->isEmpty()) {
+            return response()->json([
+                'current_user' => new UserResource($current_user),
+                'current_user_settings' => $current_user_settings,
+                'current_user_abilities' => [],
+                'companies' => [],
+                'current_company' => null,
+                'current_company_settings' => [],
+                'current_company_currency' => Currency::first(),
+                'config' => config('invoiceshelf'),
+                'global_settings' => $global_settings,
+                'main_menu' => [],
+                'setting_menu' => [],
+                'modules' => [],
+                'pending_invitations' => CompanyInvitationResource::collection($pendingInvitations),
+            ]);
+        }
 
         $main_menu = $this->generateMenu('main_menu', $current_user);
-
         $setting_menu = $this->generateMenu('setting_menu', $current_user);
 
-        $companies = $current_user->companies;
-
         $current_company = Company::find($request->header('company'));
 
         if ((! $current_company) || ($current_company && ! $current_user->hasCompany($current_company->id))) {
@@ -49,18 +85,6 @@ class BootstrapController extends Controller
 
         BouncerFacade::refreshFor($current_user);
 
-        $global_settings = Setting::getSettings([
-            'api_token',
-            'admin_portal_theme',
-            'admin_portal_logo',
-            'login_page_logo',
-            'login_page_heading',
-            'login_page_description',
-            'admin_page_title',
-            'copyright_text',
-            'save_pdf_to_disk',
-        ]);
-
         return response()->json([
             'current_user' => new UserResource($current_user),
             'current_user_settings' => $current_user_settings,
@@ -74,6 +98,7 @@ class BootstrapController extends Controller
             'main_menu' => $main_menu,
             'setting_menu' => $setting_menu,
             'modules' => Module::where('enabled', true)->pluck('name'),
+            'pending_invitations' => CompanyInvitationResource::collection($pendingInvitations),
         ]);
     }
 

app/Http/Controllers/Company/General/InvitationResponseController.php

@@ -0,0 +1,49 @@
+<?php
+
+namespace App\Http\Controllers\Company\General;
+
+use App\Http\Controllers\Controller;
+use App\Http\Resources\CompanyInvitationResource;
+use App\Models\CompanyInvitation;
+use App\Services\InvitationService;
+use Illuminate\Http\JsonResponse;
+use Illuminate\Http\Request;
+
+class InvitationResponseController extends Controller
+{
+    public function __construct(
+        private readonly InvitationService $invitationService,
+    ) {}
+
+    /**
+     * Get pending invitations for the authenticated user.
+     */
+    public function pending(Request $request): JsonResponse
+    {
+        $invitations = $this->invitationService->getPendingForUser($request->user());
+
+        return response()->json([
+            'invitations' => CompanyInvitationResource::collection($invitations),
+        ]);
+    }
+
+    /**
+     * Accept a company invitation.
+     */
+    public function accept(Request $request, CompanyInvitation $invitation): JsonResponse
+    {
+        $this->invitationService->accept($invitation, $request->user());
+
+        return response()->json(['success' => true]);
+    }
+
+    /**
+     * Decline a company invitation.
+     */
+    public function decline(Request $request, CompanyInvitation $invitation): JsonResponse
+    {
+        $this->invitationService->decline($invitation, $request->user());
+
+        return response()->json(['success' => true]);
+    }
+}