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/lib/components/EditableInstructions.svelte

@@ -1,13 +1,16 @@
 <script lang="ts">
-	import { createEventDispatcher } from 'svelte';
-
-	export let instructions: any[] = [];
-	export let translationMetadata: any[] | null | undefined = null;
-
-	const dispatch = createEventDispatcher();
+	let {
+		instructions = $bindable([]),
+		translationMetadata = null,
+		onchange
+	}: {
+		instructions?: any[],
+		translationMetadata?: any[] | null | undefined,
+		onchange?: (detail: { instructions: any[] }) => void
+	} = $props();
 
 	function handleChange() {
-		dispatch('change', { instructions });
+		onchange?.({ instructions });
 	}
 
 	function updateInstructionGroupName(groupIndex: number, event: Event) {