perf: lazy-load zxcvbn password library to reduce initial bundle size

- Dynamic import zxcvbn (820KB) in PasswordStrengthMeter so it only
  loads when user starts typing a password
- Raise chunkSizeWarningLimit to 850KB for the lazy-loaded chunk

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

vite.config.ts

@@ -4,6 +4,9 @@ import tailwindcss from '@tailwindcss/vite';
 import { defineConfig } from 'vite';
 
 export default defineConfig({
+	build: {
+		chunkSizeWarningLimit: 850
+	},
 	plugins: [
 		tailwindcss(),
 		sveltekit(),