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>

composer.json

@@ -20,6 +20,7 @@
         "nelmio/security-bundle": "^3.9",
         "phpdocumentor/reflection-docblock": "^6.0",
         "phpstan/phpdoc-parser": "^2.3",
+        "spomky-labs/pwa-bundle": "^1.5",
         "stevenmaguire/oauth2-keycloak": "^6.1",
         "stripe/stripe-php": "*",
         "symfony/amazon-mailer": "8.0.*",
@@ -91,7 +92,8 @@
     "scripts": {
         "auto-scripts": {
             "cache:clear": "symfony-cmd",
-            "assets:install %PUBLIC_DIR%": "symfony-cmd"
+            "assets:install %PUBLIC_DIR%": "symfony-cmd",
+            "importmap:install": "symfony-cmd"
         },
         "post-install-cmd": [
             "@auto-scripts"