refactor: Standardize data processing and update to Svelte 5 runes

This commit introduces a major refactoring of the data processing logic across multiple modules (events, archives, posts, sponsorships) to use a standardized pattern with . This improves consistency and maintainability.

Key changes:
- Replaced module-specific data processing with a generic helper.
- Removed deprecated  functions.
- Updated Svelte components to leverage the new Svelte 5 runes, simplifying state management.
- Fixed linting errors and updated test configurations.
- Added .

tests/example.test.ts

@@ -1,7 +1,7 @@
 import { test, expect } from '@playwright/test';
 
-test('has title', async ({ page }) => {
-  await page.goto('http://localhost:4173/');
+test('homepage has title and link', async ({ page }) => {
+  await page.goto('http://scott.localhost:5173/');
 
   // Expect a title "to contain" a substring.
   await expect(page).toHaveTitle(/SvelteKit/);