Spelling: "succesfull" → "successful" in user-visible strings

# Upstream issue draft — DonutsNL/samlSSO

**File at:** https://github.com/DonutsNL/samlSSO/issues/new
**Version affected:** 1.3.1
**Type:** bug (cosmetic)

---

## Title

`Spelling: "succesfull" → "successful" in user-visible strings`

## Body

**Version:** samlSSO 1.3.1 (GLPI 11)

### What happens

After a successful SAML login, the interstitial page that bounces the user into GLPI has
the title **`Auth succesfull`**. It's brief, but it lands in the browser tab on every
single sign-in, so in practice every user sees it every day.

`src/LoginFlow.php:898`

```php
\htmlescape($url),
'Auth succesfull'
);
```

### Two more, admin-facing

The same misspelling appears in two configuration strings:

- `src/LoginFlow/LoginFlowItem.php:263`
`__('Forces samlSSO to (re)apply the rules on each succesfull auth.', PLUGIN_NAME)`
- `templates/configForm/provider.html.twig:66`
`__('... This url is called by the identity provider after succesfull login.', plugin)`

### Suggested change

`succesfull` → `successful` in those three strings.

There are further instances in code comments, `changelog.md`, and the vendored
`robrichards/xmlseclibs` copies (`succesful`). I'd suggest leaving the vendored ones alone
— they belong to that project — and the comments are a judgement call. The three above are
the ones a human actually reads.

### Note on translations

`LoginFlowItem.php` and `provider.html.twig` pass these through `__()`, so changing the
source string will orphan any existing `.po` entries keyed on the old spelling. If that
matters for your release cadence, it might be worth batching with other string changes.
`LoginFlow.php:898` is a plain literal and has no such concern.

Happy to open a PR if useful.

Review the three named locations: src/LoginFlow.php:898, src/LoginFlow/LoginFlowItem.php:263, and templates/configForm/provider.html.twig:66. Replace the user-visible misspelling in those strings, consider the noted .po translation keys, and verify the three messages use “successful” while leaving vendored copies and comments unchanged.

Written by the indexing model from the issue text.