Adapt deployment for Dokploy

Replace the Gitea Actions SSH deploy with a Docker image
(serversideup/php fpm-nginx) and docker-compose setup. Store the
SQLite database inside the persistent storage volume, trust the
reverse proxy, and move admin credentials into config so they work
with cached configuration.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docker-compose.yml

@@ -0,0 +1,15 @@
+services:
+  app:
+    build:
+      context: .
+      dockerfile: Dockerfile
+    restart: unless-stopped
+    env_file:
+      - .env
+    expose:
+      - "8080"
+    volumes:
+      - storage:/var/www/html/storage
+
+volumes:
+  storage: