added frontend and made it usable

frontend/Dockerfile

@@ -0,0 +1,16 @@
+FROM php:8.3-cli
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+        libpq-dev unzip git \
+    && docker-php-ext-install pdo_pgsql \
+    && curl -sS https://getcomposer.org/installer | php -- --install-dir=/usr/local/bin --filename=composer \
+    && rm -rf /var/lib/apt/lists/*
+
+# The imported event data and the site's audience are both German-local;
+# default to that instead of the container's UTC so any future "now"/
+# "today" computation doesn't quietly disagree with the data for the two
+# hours after every UTC midnight.
+ENV TZ=Europe/Berlin
+RUN echo "date.timezone = Europe/Berlin" > /usr/local/etc/php/conf.d/timezone.ini
+
+WORKDIR /app