feat: implement discount and transport features in the quote system

- Added maximum discount settings configurable by the administrator.
- Implemented discount calculations in the quote confirmation process.
- Introduced transport options with associated costs, including handling for exceeding maximum piece limits.
- Updated frontend to display discounts and transport information in the quote summary.
- Created new database migrations for storing discount and transport settings.
- Developed a new Filament page for managing global discount settings.
- Enhanced email templates to include discount and transport details.
- Added tests to ensure proper functionality of discounts and transport calculations.

backoffice/database/migrations/2026_10_20_100000_add_sconti_to_clienti_e_preventivi.php

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+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\DB;
+use Illuminate\Support\Facades\Schema;
+
+/**
+ * Scontistica sul preventivo: il cliente applica, prima dell'invio, un 1° sconto sull'imponibile e
+ * un 2° sconto extra sul totale già scontato, entro i massimi decisi dall'amministratore.
+ * Massimi null = regola base (config preventivi.sconti); sconti_abilitati = false li disattiva.
+ */
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::table('clienti', function (Blueprint $table) {
+            $table->boolean('sconti_abilitati')->default(true)->after('password');
+            $table->decimal('sconto_max_1', 5, 2)->nullable()->after('sconti_abilitati');
+            $table->decimal('sconto_max_2', 5, 2)->nullable()->after('sconto_max_1');
+        });
+
+        Schema::table('preventivi', function (Blueprint $table) {
+            $table->decimal('subtotale', 10, 2)->default(0)->after('stato');
+            $table->decimal('sconto_1', 5, 2)->default(0)->after('subtotale');
+            $table->decimal('sconto_2', 5, 2)->default(0)->after('sconto_1');
+        });
+
+        // Preventivi esistenti: nessuno sconto, il subtotale coincide con il totale.
+        DB::table('preventivi')->update(['subtotale' => DB::raw('totale')]);
+    }
+
+    public function down(): void
+    {
+        Schema::table('clienti', function (Blueprint $table) {
+            $table->dropColumn(['sconti_abilitati', 'sconto_max_1', 'sconto_max_2']);
+        });
+
+        Schema::table('preventivi', function (Blueprint $table) {
+            $table->dropColumn(['subtotale', 'sconto_1', 'sconto_2']);
+        });
+    }
+};

backoffice/database/migrations/2026_10_20_110000_add_trasporto_to_preventivi.php

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+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+/**
+ * Contributo trasporto scelto al checkout (chiave di config preventivi.trasporto.zone): importo
+ * per pezzo x pezzi, aggiunto dopo gli sconti. Importo null = da quantificare (zona "Altro").
+ */
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::table('preventivi', function (Blueprint $table) {
+            $table->string('trasporto', 50)->nullable()->after('sconto_2');
+            $table->decimal('trasporto_importo', 10, 2)->nullable()->after('trasporto');
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::table('preventivi', function (Blueprint $table) {
+            $table->dropColumn(['trasporto', 'trasporto_importo']);
+        });
+    }
+};

backoffice/database/migrations/2026_10_20_120000_create_impostazioni_table.php

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+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Facades\Schema;
+
+/**
+ * Impostazioni globali modificabili dal backoffice (chiave => valore), es. la regola base di
+ * scontistica. Una chiave assente ricade sul valore in config/preventivi.php.
+ */
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::create('impostazioni', function (Blueprint $table) {
+            $table->id();
+            $table->string('chiave')->unique();
+            $table->json('valore')->nullable();
+            $table->timestamps();
+        });
+    }
+
+    public function down(): void
+    {
+        Schema::dropIfExists('impostazioni');
+    }
+};