v2.6.1d (Lyra): Plugin i18n, plugin editor vernieuwd, media invoegen

Plugin internationalisatie: plugins hebben eigen language/ mappen. Systeem
plugins volgen admin taal (admin.php), content plugins volgen content taal
(site.php). Fallback chain: geselecteerd -> plugin default_language -> CMS
default. PluginManager/AdminPluginAPI/CMSAPI uitgebreid met
getPluginTranslations()/t(). plugin.json settings ondersteunen
label_key/help_key/option_label_key.

Plugin uniformiteit: alle 6 plugins hebben uniforme structuur (README.md,
assets/.gitkeep, language/nl|en/). plugins/README.md herschreven.
guide plugin-development.md (NL+EN) volledig herschreven.

Plugin editor vernieuwd: geneste bestandsbrowser zijbalk, nieuw bestand
aanmaken, uploaden naar assets/, verwijderen en verplaatsen. Nieuwe routes:
plugins-file-upload, plugins-file-delete, plugins-file-move. Path-traversal
bescherming + protected plugins geblokkeerd.

Media invoegen in editor: nieuw /admin/media-list JSON endpoint + herbruikbare
_media-modal.twig include. Plugin-context scant assets/ map. editor-toolbar.js
modeMap uitgebreid voor css/scss/js/json.

Plugin overzicht knoppen: alleen iconen met title/aria-label.

Tests: pentest 30/30, WCAG 2.1 AA 25/25.

guide/en/codepress-developer/architectuur.md

@@ -4,7 +4,7 @@
 codepress/
 ├── cms/core/                # Core engine
 │   ├── class/               # CodePressCMS, ThemeManager, Logger, Analytics
-│   ├── plugin/              # PluginManager, CMSAPI, AdminPluginAPI
+│   ├── plugin/              # PluginManager, PluginAPIInterface, CMSAPI, AdminPluginAPI
 │   ├── config.php           # Config loader
 │   └── index.php            # Bootstrap
 ├── admin/                   # Admin console
@@ -13,12 +13,22 @@ codepress/
 │   └── theme/default/views/ # Twig templates
 ├── themes/                  # Themes (default, ...)
 ├── plugins/                 # Plugins (Dashboard, HTMLBlock, Navigation, ...)
+│   └── <Plugin>/            # Each plugin has:
+│       ├── <Plugin>.php     # Main class
+│       ├── plugin.json      # Metadata + settings
+│       ├── README.md        # Documentation
+│       ├── assets/          # CSS/JS/SCSS
+│       └── language/        # Plugin translations (nl/, en/, ...; admin.php/site.php)
 ├── content/                 # Content files (.md, .php, .html)
-├── language/                # Language files (nl/, en/, de/)
+├── language/                # Core CMS language files (nl/, en/, de/; site.php + admin.php)
 ├── guide/                   # Guides (nl/, en/)
 ├── public/                  # Web root
 │   ├── index.php            # Website entry point
 │   └── admin.php            # Admin entry point + router
 ├── config.json              # Site configuration
 └── version.php              # Version info
-```
+```
+
+## Plugin i18n
+
+Plugins have their own `language/` directory with translations. System plugins follow the admin language (`language/<lang>/admin.php`), content plugins follow the content language (`language/<lang>/site.php`). Fallback chain: selected language → plugin `default_language` → CMS site default → empty array. See `guide/en/codepress-developer/plugin-development.md` for details.