chore: 将后端移动到 api/ 目录，准备合并为单仓库

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

api/static/admin/js/vendor/select2/i18n/nl.js

@@ -0,0 +1,3 @@
+/*! Select2 4.0.13 | https://github.com/select2/select2/blob/master/LICENSE.md */
+
+!function(){if(jQuery&&jQuery.fn&&jQuery.fn.select2&&jQuery.fn.select2.amd)var e=jQuery.fn.select2.amd;e.define("select2/i18n/nl",[],function(){return{errorLoading:function(){return"De resultaten konden niet worden geladen."},inputTooLong:function(e){return"Gelieve "+(e.input.length-e.maximum)+" karakters te verwijderen"},inputTooShort:function(e){return"Gelieve "+(e.minimum-e.input.length)+" of meer karakters in te voeren"},loadingMore:function(){return"Meer resultaten laden…"},maximumSelected:function(e){var n=1==e.maximum?"kan":"kunnen",r="Er "+n+" maar "+e.maximum+" item";return 1!=e.maximum&&(r+="s"),r+=" worden geselecteerd"},noResults:function(){return"Geen resultaten gevonden…"},searching:function(){return"Zoeken…"},removeAllItems:function(){return"Verwijder alle items"}}}),e.define,e.require}();