feat: add PersonMultiSelect component for chip-based multi-person selection

Replaces the native multi-select pattern with a typeahead + dismissible
chips UI. Uses fixed dropdown positioning (same getBoundingClientRect
trick as PersonTypeahead) to escape overflow:hidden parents.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/lib/components/PersonMultiSelect.svelte

@@ -0,0 +1,117 @@
+<script lang="ts">
+    type Person = { id?: string; firstName?: string; lastName?: string; alias?: string };
+
+    export let selectedPersons: Person[] = [];
+
+    let searchTerm = '';
+    let results: Person[] = [];
+    let showDropdown = false;
+    let loading = false;
+    let debounceTimer: ReturnType<typeof setTimeout>;
+    let inputEl: HTMLInputElement;
+    let dropdownStyle = '';
+
+    function updateDropdownPosition() {
+        if (!inputEl) return;
+        const rect = inputEl.getBoundingClientRect();
+        dropdownStyle = `position:fixed;top:${rect.bottom + 4}px;left:${rect.left}px;width:${rect.width}px`;
+    }
+
+    function handleInput() {
+        showDropdown = true;
+        clearTimeout(debounceTimer);
+        debounceTimer = setTimeout(async () => {
+            if (searchTerm.length < 1) { results = []; return; }
+            loading = true;
+            try {
+                const res = await fetch(`/api/persons?q=${encodeURIComponent(searchTerm)}`);
+                if (res.ok) {
+                    const all: Person[] = await res.json();
+                    results = all.filter(p => !selectedPersons.some(s => s.id === p.id));
+                }
+            } catch { results = []; }
+            finally { loading = false; }
+        }, 300);
+    }
+
+    function selectPerson(person: Person) {
+        selectedPersons = [...selectedPersons, person];
+        searchTerm = '';
+        showDropdown = false;
+        results = [];
+    }
+
+    function removePerson(id: string | undefined) {
+        selectedPersons = selectedPersons.filter(p => p.id !== id);
+    }
+
+    function clickOutside(node: HTMLElement) {
+        const handleClick = (e: MouseEvent) => {
+            if (node && !node.contains(e.target as Node) && !(e as Event).defaultPrevented) {
+                showDropdown = false;
+            }
+        };
+        document.addEventListener('click', handleClick, true);
+        return { destroy() { document.removeEventListener('click', handleClick, true); } };
+    }
+</script>
+
+<svelte:window on:scroll={updateDropdownPosition} on:resize={updateDropdownPosition} />
+
+{#each selectedPersons as person}
+    <input type="hidden" name="receiverIds" value={person.id} />
+{/each}
+
+<div class="relative" use:clickOutside>
+    <div class="flex flex-wrap gap-2 p-2 border border-gray-300 rounded bg-white min-h-[42px] focus-within:ring-1 focus-within:ring-brand-navy focus-within:border-brand-navy">
+        {#each selectedPersons as person}
+            <span class="inline-flex items-center gap-1 bg-brand-sand/40 text-brand-navy text-sm font-medium px-2 py-1 rounded">
+                {person.firstName} {person.lastName}
+                <button
+                    type="button"
+                    on:click={() => removePerson(person.id)}
+                    class="text-brand-navy/50 hover:text-red-500 focus:outline-none ml-0.5"
+                    aria-label="Entfernen"
+                >
+                    <svg class="w-3 h-3" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+                        <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M6 18L18 6M6 6l12 12"/>
+                    </svg>
+                </button>
+            </span>
+        {/each}
+
+        <input
+            bind:this={inputEl}
+            type="text"
+            autocomplete="off"
+            bind:value={searchTerm}
+            on:input={handleInput}
+            on:focus={() => { updateDropdownPosition(); showDropdown = true; }}
+            placeholder={selectedPersons.length === 0 ? 'Namen tippen...' : ''}
+            class="flex-1 min-w-[120px] border-none p-1 focus:ring-0 text-sm bg-transparent outline-none"
+        />
+    </div>
+
+    {#if showDropdown && (results.length > 0 || loading)}
+        <div
+            style={dropdownStyle}
+            class="z-50 bg-white shadow-lg max-h-60 rounded-md py-1 text-base ring-1 ring-black ring-opacity-5 overflow-auto sm:text-sm"
+        >
+            {#if loading}
+                <div class="p-2 text-gray-500 text-sm">Suche...</div>
+            {:else}
+                {#each results as person}
+                    <!-- svelte-ignore a11y-click-events-have-key-events -->
+                    <div
+                        class="cursor-pointer select-none py-2 pl-3 pr-9 hover:bg-brand-sand/30 text-gray-900"
+                        on:click={() => selectPerson(person)}
+                        role="button"
+                        tabindex="0"
+                    >
+                        {person.lastName}, {person.firstName}
+                    </div>
+                {/each}
+            {/if}
+        </div>
+    {/if}
+</div>