chore : rename Coltura to Starseed

- Rename project name across code, configs, docs, dev/prod infra
- Dev: DOCKER_APP_NAME + POSTGRES_DB switched to starseed, containers become php-starseed-fpm / nginx-starseed / starseed-db-1
- Dev: mount nginx.conf on default.conf instead of starseed.conf to avoid alphabetical-order clash with image's default site
- Makefile: export CURRENT_UID/CURRENT_GID at top level so docker compose builds (db-reset etc.) get them
- Prod: image registry path, container_name, volumes, vhost server_name + paths, DATABASE_URL, CORS, CI workflow
- Add doc/prompt-rename-prod.md with the migration runbook for the prod server (DB rename, FS move, vhost, Let's Encrypt)

infra/prod/nginx-proxy.conf

@@ -1,12 +1,12 @@
 server {
     listen 80;
     listen [::]:80;
-    server_name coltura.malio-dev.fr;
+    server_name starseed.malio-dev.fr;
 
-    root /var/www/coltura/public;
+    root /var/www/starseed/public;
 
     # Maintenance mode
-    if (-f /var/www/coltura/maintenance.on) {
+    if (-f /var/www/starseed/maintenance.on) {
         return 503;
     }