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

database/migrations/2025_11_21_081606_create_notes_table.php

@@ -0,0 +1,36 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+return new class extends Migration
+{
+    /**
+     * Run the migrations.
+     */
+    public function up(): void
+    {
+        Schema::create('notes', function (Blueprint $table) {
+            $table->id();
+            $table->foreignId('user_id')->constrained()->nullOnDelete();
+            $table->text('text');
+            
+            // Polymorphische Beziehung
+            $table->unsignedBigInteger('notable_id');
+            $table->string('notable_type');
+
+            $table->timestamps();
+
+            $table->index(['user_id', 'notable_id', 'notable_type']);
+        });
+    }
+
+    /**
+     * Reverse the migrations.
+     */
+    public function down(): void
+    {
+        Schema::dropIfExists('notes');
+    }
+};