Add pcntl/posix PHP extensions for Reverb signal handling

The Reverb websocket server (artisan reverb:start) needs pcntl for
SIGINT/SIGTERM/SIGTSTP signal handling on shutdown; the base php:apache
image doesn't enable it by default.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Dockerfile

@@ -8,7 +8,7 @@ RUN apt-get update && apt-get install -y \
     unzip \
     git \
     libldap2-dev \
-    && docker-php-ext-install curl mysqli pdo pdo_mysql ldap zip
+    && docker-php-ext-install curl mysqli pdo pdo_mysql ldap zip pcntl posix
 
 # Kopiowanie Composera z oficjalnego obrazu
 COPY --from=composer:latest /usr/bin/composer /usr/bin/composer