chore(infra): set BODY_SIZE_LIMIT=50M in frontend service

Makes the upload size cap explicit in both dev and prod compose files.
After the @sveltejs/kit bump (GHSA-2crg-3p73-43xp), the default 512KB
limit is now enforced — 50M covers multi-page Kurrent/Sütterlin PDFs
(typically 500KB–15MB) without being reckless.

Caddy's client_max_body_size must be set to match when the reverse
proxy config is committed.

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

docker-compose.prod.yml

@@ -276,6 +276,9 @@ services:
       # SSR fetches go inside the docker network; clients hit https://${APP_DOMAIN}
       API_INTERNAL_URL: http://backend:8080
       ORIGIN: https://${APP_DOMAIN}
+      # Enforce upload size limit in the adapter-node layer (fixes GHSA-2crg-3p73-43xp bypass).
+      # Must be ≤ client_max_body_size in the Caddy reverse proxy to avoid 413 mismatches.
+      BODY_SIZE_LIMIT: 50M
     networks:
       - archiv-net
     healthcheck:

docker-compose.yml

@@ -228,6 +228,9 @@ services:
       API_INTERNAL_URL: http://backend:8080
       # Vite dev proxy forwards /api from browser to the backend container
       API_PROXY_TARGET: http://backend:8080
+      # Upload size limit for adapter-node (production target). Not enforced by Vite dev server
+      # but kept here to match docker-compose.prod.yml and prevent config drift.
+      BODY_SIZE_LIMIT: 50M
     ports:
       - "${PORT_FRONTEND}:5173"
     networks: