refactor: migrate all Svelte components from Svelte 4 to Svelte 5 runes

- Replace `export let` with `$props()` and `$bindable()` across all components
- Replace `$:` reactive statements with `$derived()` and `$effect()`
- Replace `createEventDispatcher` with callback props (e.g. `onchange`)
- Replace `on:event` directives with inline event handlers (`onclick`, `oninput`, etc.)
- Replace `<slot />` with `{@render children()}` in layout
- Use `untrack()` for SSR-safe $state initialization from reactive props
- Replace `blur` + `setTimeout` anti-pattern in TagInput with `clickOutside` action
- Fix `page` store usage in layout to use `$app/state` directly
- 0 errors, 0 warnings after svelte-check

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

frontend/src/routes/persons/new/+page.svelte

@@ -1,5 +1,5 @@
 <script lang="ts">
-export let form;
+let { form } = $props();
 </script>
 
 <div class="mx-auto max-w-2xl px-4 py-8">