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.

resources/views/components/modal-confirmation.blade.php

@@ -35,7 +35,7 @@
     $skipPasswordConfirmation = shouldSkipPasswordConfirmation();
     if ($temporaryDisableTwoStepConfirmation) {
         $disableTwoStepConfirmation = false;
-        $skipPasswordConfirmation = false;
+        // Password confirmation requirement is not affected by temporary two-step disable
     }
     // When password step is skipped, Step 2 becomes final - change button text from "Continue" to "Confirm"
     $effectiveStep2ButtonText = ($skipPasswordConfirmation && $step2ButtonText === 'Continue') ? 'Confirm' : $step2ButtonText;