chore(ci): setup Gitea Actions + Portainer auto-deploy pipeline

.env.docker

@@ -0,0 +1,13 @@
+# Dummy environment for Docker build stage
+# These values are only needed so Next.js can compile during docker build
+# Runtime values are injected via docker-compose environment
+DATABASE_URL=postgresql://lageplan:lageplan_secret@db:5432/lageplan
+NEXTAUTH_URL=http://localhost:3000
+NEXTAUTH_SECRET=build-time-secret-not-used-at-runtime
+MINIO_ENDPOINT=minio
+MINIO_PORT=9000
+MINIO_ACCESS_KEY=minioadmin
+MINIO_SECRET_KEY=minioadmin123
+MINIO_BUCKET=lageplan-icons
+MINIO_USE_SSL=false
+MINIO_PUBLIC_URL=http://localhost:9000