feat: complete Svelte 5 migration across entire application

Migrated all components and routes from Svelte 4 to Svelte 5 syntax:

- Converted export let → $props() with generic type syntax
- Replaced createEventDispatcher → callback props
- Migrated $: reactive statements → $derived() and $effect()
- Updated two-way bindings with $bindable()
- Fixed TypeScript syntax: added lang="ts" to script tags
- Converted inline type annotations to generic parameter syntax

- Updated deprecated event directives to Svelte 5 syntax:
  - on:click → onclick
  - on:submit → onsubmit
  - on:change → onchange

- Converted deprecated <slot> elements → {@render children()}
- Updated slot props to Snippet types
- Fixed season/icon selector components with {#snippet} blocks

- Fixed non-reactive state by converting let → $state()
- Fixed infinite loop in EnhancedBalance by converting $effect → $derived
- Fixed Chart.js integration by converting $state proxies to plain arrays
- Updated cospend dashboard and payment pages with proper reactivity

- Migrated 20+ route files from export let data → $props()
- Fixed TypeScript type annotations in page components
- Updated reactive statements in error and cospend routes

- Removed invalid onchange attribute from Toggle component
- Fixed modal ID isolation in CreateIngredientList/CreateStepList
- Fixed dark mode button visibility in TranslationApproval
- Build now succeeds with zero deprecation warnings

All functionality tested and working. No breaking changes to user experience.

src/routes/+error.svelte

@@ -3,15 +3,15 @@
   import { goto } from '$app/navigation';
   import Header from '$lib/components/Header.svelte';
 
-  $: status = $page.status;
-  $: error = $page.error;
+  let status = $derived($page.status);
+  let error = $derived($page.error);
 
   // Get session data if available (may not be available in error context)
-  $: session = $page.data?.session;
-  $: user = session?.user;
+  let session = $derived($page.data?.session);
+  let user = $derived(session?.user);
 
   // Get Bible quote from SSR via handleError hook
-  $: bibleQuote = $page.error?.bibleQuote;
+  let bibleQuote = $derived($page.error?.bibleQuote);
 
   function getErrorTitle(status) {
     switch (status) {