feat(pwa): remove SvelteKitPWA plugin dependencies

Story 2: Remove SvelteKitPWA Plugin Dependencies
- Remove @vite-pwa/sveltekit from package.json dependencies
- Remove SvelteKitPWA plugin import and configuration from vite.config.ts
- Clean up plugin configuration including manifest, workbox, and devOptions
- Build process now works without plugin (service worker migration needed next)

Dependencies reduced by 309 packages
Build fails on workbox imports as expected - ready for Story 3

Refs: docs/plans/MigrateToNativeSvelteKitPWA.md

package.json

@@ -23,7 +23,6 @@
         "@sveltejs/vite-plugin-svelte": "^6.2.1",
         "@tailwindcss/vite": "^4.1.17",
         "@types/node": "^22",
-        "@vite-pwa/sveltekit": "^0.3.0",
         "@vitest/browser-playwright": "^4.0.10",
         "eslint": "^9.39.1",
         "eslint-config-prettier": "^10.1.8",