Make server deployable with Docker Compose on Coolify

- Read bind address and database URL from BIND_ADDR / DATABASE_URL
  (defaults unchanged for local cargo run)
- Rename DockerFile to Dockerfile and rewrite it: current Rust for
  edition 2024, BuildKit cache mounts, non-root user, DB on /data
- Add compose.yaml publishing ${HOST_PORT:-8080} with a persistent
  data volume, and a .dockerignore

Co-Authored-By: Claude Opus 5.5 <[email protected]>

compose.yaml

@@ -0,0 +1,13 @@
+services:
+  server:
+    build: .
+    restart: unless-stopped
+    # Published on the host (HOST_PORT, default 8080) and still reachable by
+    # Coolify's proxy; set the domain in Coolify as https://<domain>:8080.
+    ports:
+      - "${HOST_PORT:-8080}:8080"
+    volumes:
+      - server-data:/data
+
+volumes:
+  server-data: