Add per-form Listmonk list UUIDs to newsletter plugin

Add support for specifying Listmonk list UUIDs per form instance
Update petition form to use metadata-defined UUIDs
Add success confirmation message to newsletter forms
Update documentation with new functionality

docs/newsletter-plugin.md

@@ -17,6 +17,7 @@ Then call from PHP content files:
 ```php
 <?= newsletter_signup('Your custom intro text here', 'hero') ?>
 <?= newsletter_signup('Short text here', 'small') ?>
+<?= newsletter_signup('Text', 'small', ['list-uuid-1', 'list-uuid-2']) ?>
 ```
 
 ## Themes
@@ -29,11 +30,12 @@ Then call from PHP content files:
 ## Function Signature
 
 ```php
-newsletter_signup(string $introText, string $theme = 'hero', string $formId = 'newsletter'): string
+newsletter_signup(string $introText, string $theme = 'hero', array $listUuids = [], string $formId = 'newsletter'): string
 ```
 
 - `$introText` - Displayed above the form
 - `$theme` - `'hero'` or `'small'`
+- `$listUuids` - Listmonk list UUIDs for this form (empty = use global config)
 - `$formId` - HTML id for the section (for anchor links)
 
 ## How It Works
@@ -58,6 +60,8 @@ return [
 
 Uses Listmonk's **public** subscription API (`/api/public/subscription`). No authentication needed. Listmonk handles its own double opt-in flow.
 
+Per-form list UUIDs can be passed via `$listUuids` parameter. When empty, falls back to the global config's `list_uuids`.
+
 ## Anti-Spam
 
 1. **CSRF token** - Separate from petition (`newsletter_csrf_token`)
@@ -71,7 +75,7 @@ All use `newsletter.*` prefix in language files:
 - `newsletter.email_label`, `newsletter.email_placeholder`
 - `newsletter.notice` (e.g., "We send about 12 emails per year")
 - `newsletter.submit_button`
-- `newsletter.success_message`, `newsletter.error_message`
+- `newsletter.success_message`, `newsletter.success_confirm`, `newsletter.error_message`
 
 ## Static Resources