Fix: Don't overwrite Supabase postgres init scripts

Mounting to /docker-entrypoint-initdb.d was replacing the Supabase
postgres image's built-in initialization scripts that create the
auth schema, roles, etc. Now mounting to /migrations instead.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docker-compose.nginx.yml

@@ -27,7 +27,9 @@ services:
       JWT_EXP: ${JWT_EXPIRY}
     volumes:
       - db-data:/var/lib/postgresql/data
-      - ./supabase/migrations:/docker-entrypoint-initdb.d
+      # Migrations are mounted separately - run them manually after DB is initialized
+      # DO NOT mount to /docker-entrypoint-initdb.d as it overwrites Supabase's init scripts
+      - ./supabase/migrations:/migrations:ro
     healthcheck:
       test: ["CMD-SHELL", "pg_isready -U postgres"]
       interval: 10s