fix(docker): align www-data UID/GID with host (1000:1000)

php-fpm runs workers as www-data, so master stays root and drops to a UID matching host files. storage bind-mount is writable without runtime chmod hacks.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Dockerfile

@@ -1,13 +1,19 @@
 FROM php:8.4-fpm-alpine AS base
 
+ARG HOST_UID=1000
+ARG HOST_GID=1000
+
 RUN apk add --no-cache \
         libzip-dev \
         zlib-dev \
         unzip \
         git \
         curl \
+        shadow \
     && docker-php-ext-install zip pcntl \
-    && curl -sS https://getcomposer.org/installer | php -- --install-dir=/usr/local/bin --filename=composer
+    && curl -sS https://getcomposer.org/installer | php -- --install-dir=/usr/local/bin --filename=composer \
+    && groupmod -g $HOST_GID www-data \
+    && usermod -u $HOST_UID -g $HOST_GID www-data
 
 WORKDIR /var/www/html