Bind-mount the project into the container for live edits

docker-compose.yml now mounts the working directory at /var/www/html so
PHP changes take effect without an image rebuild. To avoid a mount nested
inside that bind mount, the storage directory moves out to /var/www/storage
(still a named volume). Config gains a STORAGE_PATH env var driving both the
SQLite database and the JWT signing-key location; the entrypoint chowns that
directory. The Dockerfile is unchanged and still builds a self-contained
image (STORAGE_PATH defaults back to ./storage when unset).

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

docker/entrypoint.sh

@@ -1,10 +1,11 @@
 #!/bin/sh
 set -e
 
-# The storage directory may be a freshly created named volume; make sure it
-# exists and is writable by the web-server user.
-mkdir -p storage
-chown -R www-data:www-data storage
+# Storage lives outside the app directory when the source is bind-mounted for
+# development (see docker-compose.yml); the plain image falls back to ./storage.
+STORAGE_DIR="${STORAGE_PATH:-storage}"
+mkdir -p "$STORAGE_DIR"
+chown -R www-data:www-data "$STORAGE_DIR"
 
 # Apply pending migrations as www-data so the SQLite file it creates stays
 # writable by Apache.