Add Notes model, controller and database table. Implement it in Customer Dialog, #6

database/migrations/2025_09_17_000000_create_customers_table.php

@@ -22,7 +22,6 @@ public function up()
             $table->json('billing_address')->nullable();
             $table->foreignId('payment_terms_id')->constrained()->default(3); // Standard-Zahlungsziel: 14 Tage
             $table->enum('status', ['active', 'inactive', 'prospect'])->default('active');
-            $table->text('notes')->nullable();
             $table->string('logo')->nullable();
             $table->timestamps();
         });