Full mobile responsive (320px) and tablet (768px) support across all templates

- All text-[20rem] background text → text-[8rem] md:text-[20rem]
- All text-8xl → text-5xl md:text-8xl
- All text-5xl emojis → text-3xl md:text-5xl
- edit_event: w-full md:w-[80%], poster column w-full lg:w-[350px]
- account/index: tab bar overflow-x-auto, events table overflow-x-auto
- admin/events: table overflow-x-auto
- register: tab buttons overflow-x-auto
- error 404/500: responsive padding p-6 md:p-12
- base footer: flex-col sm:flex-row for bottom bar
- Add PWA bundle (spomky-labs/pwa-bundle) with composer require files

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitignore

@@ -30,3 +30,18 @@ node_modules/
 /.php-cs-fixer.php
 /.php-cs-fixer.cache
 ###< friendsofphp/php-cs-fixer ###
+
+###> symfony/asset-mapper ###
+/public/assets/
+/assets/vendor/
+###< symfony/asset-mapper ###
+
+###> spomky-labs/pwa-bundle ###
+/public/idb
+/public/pwa
+/public/workbox
+/public/favicon.ico
+/public/site.webmanifest
+/public/site.*.webmanifest
+/public/sw.js
+###< spomky-labs/pwa-bundle ###