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>

.dockerignore

@@ -0,0 +1,24 @@
+.git
+.idea
+.vscode
+.env
+.env.*
+!.env.example
+.phpunit.result.cache
+.phpunit.cache
+node_modules
+vendor
+public/build
+public/hot
+public/storage
+bootstrap/cache/*.php
+storage/logs/*
+storage/framework/cache/data/*
+storage/framework/sessions/*
+storage/framework/views/*
+storage/app/private/*
+storage/app/public/*
+database/*.sqlite
+test.html
+docker-compose.yml
+Dockerfile