fix(subscription): harden quantity updates and proxy trust behavior

Centralize min/max server limits in Stripe quantity updates and wire them into
Livewire subscription actions with price preview/update handling.

Also improve host/proxy middleware behavior by trusting loopback hosts when FQDN
is set and auto-enabling secure session cookies for HTTPS requests behind
proxies when session.secure is unset.

Includes feature tests for loopback trust and secure cookie auto-detection.

tests/Feature/SecureCookieAutoDetectionTest.php

@@ -0,0 +1,64 @@
+<?php
+
+use App\Models\InstanceSettings;
+use Illuminate\Support\Facades\Cache;
+
+uses(\Illuminate\Foundation\Testing\RefreshDatabase::class);
+
+beforeEach(function () {
+    Cache::forget('instance_settings_fqdn_host');
+    InstanceSettings::updateOrCreate(['id' => 0], ['fqdn' => null]);
+    // Ensure session.secure starts unconfigured for each test
+    config(['session.secure' => null]);
+});
+
+it('sets session.secure to true when request arrives over HTTPS via proxy', function () {
+    $this->get('/login', [
+        'X-Forwarded-Proto' => 'https',
+        'X-Forwarded-For' => '1.2.3.4',
+    ]);
+
+    expect(config('session.secure'))->toBeTrue();
+});
+
+it('does not set session.secure for plain HTTP requests', function () {
+    $this->get('/login');
+
+    expect(config('session.secure'))->toBeNull();
+});
+
+it('does not override explicit SESSION_SECURE_COOKIE=false for HTTPS requests', function () {
+    config(['session.secure' => false]);
+
+    $this->get('/login', [
+        'X-Forwarded-Proto' => 'https',
+        'X-Forwarded-For' => '1.2.3.4',
+    ]);
+
+    // Explicit false must not be overridden — our check is `=== null` only
+    expect(config('session.secure'))->toBeFalse();
+});
+
+it('does not override explicit SESSION_SECURE_COOKIE=true', function () {
+    config(['session.secure' => true]);
+
+    $this->get('/login');
+
+    expect(config('session.secure'))->toBeTrue();
+});
+
+it('marks session cookie with Secure flag when accessed over HTTPS proxy', function () {
+    $response = $this->get('/login', [
+        'X-Forwarded-Proto' => 'https',
+        'X-Forwarded-For' => '1.2.3.4',
+    ]);
+
+    $response->assertSuccessful();
+
+    $cookieName = config('session.cookie');
+    $sessionCookie = collect($response->headers->all('set-cookie'))
+        ->first(fn ($c) => str_contains($c, $cookieName));
+
+    expect($sessionCookie)->not->toBeNull()
+        ->and(strtolower($sessionCookie))->toContain('; secure');
+});