implemented reflection of kanban filter in url

frontend/src/routes/project/Kanban.svelte

@@ -10,19 +10,27 @@
     import LineEditor from '../../Components/LineEditor.svelte';
 
     let { id } = $props();
-
+    let filter_input = $state('');
+    let router       = useTinyRouter();
+    if (router.hasQueryParam('filter')) filter_input = router.getQueryParam('filter');
     let dragged      = null;
     let error        = $state(null);
     let highlight    = $state({});
-    let filter_input = $state('');
     let filter       = $derived(filter_input.toLowerCase());
     let project      = $state(null);
     let ready        = $state(false);
-    let router       = useTinyRouter();
     let tasks        = $state({});
     let users        = {};
     let columns      = $derived(project.allowed_states?Object.keys(project.allowed_states).length+1:1);
 
+    $effect(() => updateUrl(filter_input));
+
+    function updateUrl(){
+        let url = window.location.origin + window.location.pathname;
+        if (filter_input) url += '?filter=' + encodeURI(filter_input);
+        window.history.replaceState(history.state, '', url);
+    }
+
     async function create(name,user_id,state){
         var url = api('task/add');
         let task = {