Add Gitea backup/restore scripts, parameterize configs

- Add gitea/backup.sh and gitea/restore.sh
- Move hardcoded values in gitea/docker-compose.yml to gitea/.env
- Move immich .env from root to immich-app/, update env_file path
- Remove root docker-compose.yml (was only an include alias)

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

immich-app/docker-compose.yml

@@ -23,7 +23,7 @@ services:
       - ${ENCODED_VIDEO_LOCATION}:/data/encoded-video
       - /etc/localtime:/etc/localtime:ro
     env_file:
-      - ../.env
+      - .env
     ports:
       - '2283:2283'
     depends_on:
@@ -44,7 +44,7 @@ services:
     volumes:
       - model-cache:/cache
     env_file:
-      - ../.env
+      - .env
     restart: always
     healthcheck:
       disable: false