fix(i18n): correct and complete Hungarian localization

[sipeti]

Summary

This fixes Hungarian UI issues found while using LibreBooking 7.1.0 and applies the corrections to current develop.

• Distinguish the Reserve action (Foglalás) from the Reserved state (Foglalt).
• Fix misspellings including Vezetkéknév, Frisstés, ELérhetőség, beisztás, and the July name Jólius.
• Correct misleading labels: Username or Email asked for a password; group roles were translated as rules; several check-in/out messages were reversed.
• Use consistent resource/calendar terminology and translate English fallback strings, mixed-language import instructions and email subjects.
• Use Hungarian year-first dates and 24-hour times across PHP, date pickers and calendar formats. Correct weekday/month names and distinguish Saturday from Sunday.
• Preserve formatting placeholders, DataTables tokens, import format tokens and literal sample credentials.

The contribution updates the native Hungarian locale and adds focused regression tests. It includes no deployment-specific authorization, Studio plugins, custom branding, account data, or calendar-name/database changes. Email body templates are outside this patch.

Validation

• PHP 8.4.20: syntax checks for both changed PHP files pass.
• PHPUnit 11.5.57: 4 tests, 2977 assertions, run with a minimal bootstrap loading only the locale (no database or application services).
• PHP CS Fixer 3.95.27: both files pass the repository's configuration.
• Hungarian locale audit: translated strings retain English substitution signatures and DataTables tokens.

The full application test suite has not been run locally. Opening as a draft for review of the Hungarian wording and upstream CI.

Manual verification

Select Hungarian, open the dashboard and a reservation form, then check:

1. The available-resource button reads Foglalás, while occupied status remains Foglalt.
2. Dates display in year-month-day order and times use the 24-hour clock.
3. Calendar settings describe the standard layout without the beisztás typo.
4. Login asks for a username or email address, and check-in/out messages describe arrival/departure rather than account login/logout.

Prepared with Codex assistance; attributed in the commit trailer per CONTRIBUTING.md.