feat(docker): migrate base image from php-cli to FrankenPHP Alpine

Replace php:8.4-cli-alpine3.21 with dunglas/frankenphp:1-php8.4-alpine.
No Go toolchain required — the official image ships as a pre-compiled
Alpine binary.

- Drop docker-php-ext-install opcache (FrankenPHP enables it by default)
- Both dev and final stages run frankenphp run --config /etc/caddy/Caddyfile
- Dev stage bakes in Caddyfile.dev (no worker mode, Xdebug compatible)
- Final stage bakes in production Caddyfile

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Dockerfile

@@ -1,10 +1,9 @@
-FROM php:8.4-cli-alpine3.21 AS base
+FROM dunglas/frankenphp:1-php8.4-alpine AS base
 
 RUN apk add --no-cache \
     curl \
     icu-libs \
-    libzip \
-    && docker-php-ext-install opcache
+    libzip
 
 WORKDIR /app
 
@@ -32,11 +31,12 @@ RUN apk add --no-cache ${PHPIZE_DEPS} linux-headers \
     && docker-php-ext-enable xdebug \
     && apk del ${PHPIZE_DEPS}
 COPY docker/php/xdebug.ini /usr/local/etc/php/conf.d/docker-xdebug.ini
+COPY docker/frankenphp/Caddyfile.dev /etc/caddy/Caddyfile
 COPY composer.json composer.lock* ./
 RUN composer install --no-scripts --no-interaction --prefer-dist
 EXPOSE 8080
 ENV APP_ENV=dev APP_DEBUG=1
-CMD ["php", "-S", "0.0.0.0:8080", "-t", "public", "public/index.php"]
+CMD ["frankenphp", "run", "--config", "/etc/caddy/Caddyfile"]
 
 # ── final (prod) stage — no composer binary ────────────────────────────────────
 FROM base AS final
@@ -45,6 +45,7 @@ RUN addgroup -S app && adduser -S -G app app
 
 COPY --from=build /app/vendor /app/vendor
 COPY . .
+COPY docker/frankenphp/Caddyfile /etc/caddy/Caddyfile
 
 RUN mkdir -p var/cache var/log \
     && chown -R app:app /app
@@ -54,4 +55,4 @@ USER app
 EXPOSE 8080
 ENV APP_ENV=prod APP_DEBUG=0
 
-CMD ["php", "-S", "0.0.0.0:8080", "-t", "public", "public/index.php"]
+CMD ["frankenphp", "run", "--config", "/etc/caddy/Caddyfile"]