Rename company-scoped Users to Members throughout

Complete rename across backend and frontend:
- Controller: Company/Users/UsersController -> Company/Members/MembersController
- Service: UserService -> MemberService
- Requests: UserRequest -> MemberRequest, DeleteUserRequest -> DeleteMemberRequest
- API routes: /api/v1/users -> /api/v1/members (company-scoped only)
- Sidebar menu: "Users" -> "Members"
- Frontend: views/users -> views/members, stores/users -> stores/members
- Router: users.index -> members.index, /admin/users -> /admin/members
- i18n: new "members" section with invitation-related keys
- Tests: UserTest -> MemberTest

Admin/super-admin Users (system-wide user management) remains unchanged.

app/Http/Requests/MemberRequest.php

@@ -0,0 +1,73 @@
+<?php
+
+namespace App\Http\Requests;
+
+use Illuminate\Foundation\Http\FormRequest;
+use Illuminate\Validation\Rule;
+
+class MemberRequest extends FormRequest
+{
+    /**
+     * Determine if the user is authorized to make this request.
+     */
+    public function authorize(): bool
+    {
+        return true;
+    }
+
+    /**
+     * Get the validation rules that apply to the request.
+     */
+    public function rules(): array
+    {
+        $rules = [
+            'name' => [
+                'required',
+            ],
+            'email' => [
+                'required',
+                'email',
+                Rule::unique('users'),
+            ],
+            'phone' => [
+                'nullable',
+            ],
+            'password' => [
+                'required',
+                'min:8',
+            ],
+            'companies' => [
+                'required',
+            ],
+            'companies.*.id' => [
+                'required',
+            ],
+            'companies.*.role' => [
+                'required',
+            ],
+        ];
+
+        if ($this->getMethod() == 'PUT') {
+            $rules['email'] = [
+                'required',
+                'email',
+                Rule::unique('users')->ignore($this->user),
+            ];
+            $rules['password'] = [
+                'nullable',
+                'min:8',
+            ];
+        }
+
+        return $rules;
+    }
+
+    public function getUserPayload()
+    {
+        return collect($this->validated())
+            ->merge([
+                'creator_id' => $this->user()->id,
+            ])
+            ->toArray();
+    }
+}