fix(deployment): change application mount to read-write, remove storage/var volume overlays

Docker named volumes cannot create mount points inside read-only directories.
Previous configuration attempted to mount storage and var-data volumes at subdirectories
inside a read-only base mount (/var/www/html:ro), causing deployment failures.

Changes:
- php service: Changed /var/www/html mount from :ro to :rw, removed storage volume
- queue-worker service: Changed mount to :rw, removed storage and var-data volumes
- scheduler service: Changed mount to :rw, removed storage and var-data volumes

Security maintained through:
- Container runs as non-root user (appuser via gosu)
- Security hardening (no-new-privileges, dropped capabilities)
- Rsync deployment from trusted source

This is the eighth cumulative fix for production deployment pipeline.

docker-compose.production.yml

@@ -146,10 +146,8 @@ services:
 
     # Production volumes
     volumes:
-      # Mount application code from rsync deployment (read-only)
-      - /home/deploy/michaelschiemer/current:/var/www/html:ro
-      # Mount storage directory as writable volume (overlays the read-only code mount)
-      - storage:/var/www/html/storage:rw
+      # Mount application code from rsync deployment (read-write for storage/var directories)
+      - /home/deploy/michaelschiemer/current:/var/www/html:rw
 
   # Database service removed - using external PostgreSQL Stack (deployment/stacks/postgresql/)
   # Connection via app-internal network using docker-compose.postgres-override.yml
@@ -244,12 +242,8 @@ services:
 
     # Production volumes
     volumes:
-      # Mount application code from rsync deployment (read-only)
-      - /home/deploy/michaelschiemer/current:/var/www/html:ro
-      # Mount storage directory as writable volume (overlays the read-only code mount)
-      - storage:/var/www/html/storage:rw
-      # Mount var directory as writable volume for cache and logs (overlays read-only code mount)
-      - var-data:/var/www/html/var:rw
+      # Mount application code from rsync deployment (read-write for storage/var directories)
+      - /home/deploy/michaelschiemer/current:/var/www/html:rw
 
     environment:
       - APP_ENV=production
@@ -317,12 +311,8 @@ services:
 
     # Production volumes
     volumes:
-      # Mount application code from rsync deployment (read-only)
-      - /home/deploy/michaelschiemer/current:/var/www/html:ro
-      # Mount storage directory as writable volume (overlays the read-only code mount)
-      - storage:/var/www/html/storage:rw
-      # Mount var directory as writable volume for cache and logs (overlays read-only code mount)
-      - var-data:/var/www/html/var:rw
+      # Mount application code from rsync deployment (read-write for storage/var directories)
+      - /home/deploy/michaelschiemer/current:/var/www/html:rw
 
     environment:
       - TZ=Europe/Berlin