Upgrade SvelteKit 4 to SvelteKit 5 with latest dependencies

Major changes:
- Upgraded Svelte from v4 to v5.38.6 (latest stable)
- Upgraded SvelteKit from v2.0.0 to v2.37.0 (latest)
- Upgraded Vite from v5 to v7.1.3 for better performance
- Updated all related packages to latest compatible versions
- Added pnpm as package manager with packageManager field
- Fixed Card.svelte nested anchor tags issue by converting inner links to buttons
- Updated component styling to maintain visual consistency
- Removed incompatible svelte-preprocess-import-assets package

Dependencies updated:
- @sveltejs/kit: ^2.0.0 → ^2.37.0
- @sveltejs/vite-plugin-svelte: ^3.0.0 → ^6.1.3
- svelte: ^4.0.0 → ^5.38.6
- vite: ^5.0.0 → ^7.1.3
- @sveltejs/adapter-auto: ^3.0.0 → ^6.1.0
- @sveltejs/adapter-node: ^2.0.0 → ^5.0.0
- svelte-check: ^3.4.6 → ^4.0.0
- mongoose: ^7.4.0 → ^8.0.0
- sharp: ^0.32.3 → ^0.33.0

🤖 Generated with [Claude Code](https://claude.ai/code)

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

src/routes/api/cospend/balance/+server.ts

@@ -0,0 +1,38 @@
+import type { RequestHandler } from '@sveltejs/kit';
+import { json } from '@sveltejs/kit';
+import { Payment } from '$lib/models/Payment'; // adjust path as needed
+import { dbConnect, dbDisconnect } from '$lib/db/db';
+
+const UPLOAD_DIR = '/var/lib/www/static/test';
+const BASE_CURRENCY = 'CHF'; // Default currency
+
+export const GET: RequestHandler = async ({ request, locals }) => {
+    await dbConnect();
+
+    const result = await Payment.aggregate([
+  {
+    $group: {
+      _id: "$paid_by",
+      totalPaid: { $sum: "$total_amount" },
+      totalForSelf: { $sum: { $ifNull: ["$for_self", 0] } },
+      totalForOther: { $sum: { $ifNull: ["$for_other", 0] } }
+    }
+  },
+  {
+    $project: {
+      _id: 0,
+      paid_by: "$_id",
+      netTotal: {
+	$multiply: [
+		{ $add: [
+          { $subtract: ["$totalPaid", "$totalForSelf"] },
+	  "$totalForOther"
+        ] },
+	0.5]
+      }
+    }
+  }
+]);
+    await dbDisconnect();
+    return json(result);
+};