Add Docker deployment support with compose, entrypoint and docs

- Add Dockerfile (pre-built binary) and Dockerfile.source
- Add docker-compose.yml, docker-compose.prod.yml, docker-compose.override.yml
- Add docker-entrypoint.sh with non-root user support
- Add .dockerignore and helper scripts (scripts/docker-build.sh, scripts/docker-run.sh)
- Add docs/en/docker.md with full Docker guide
- Update docs/en/deployment.md and README.md
- Fix src/barabadb/core/config.nim to read BARADB_ADDRESS, BARADB_PORT, BARADB_DATA_DIR from env
- Fix src/barabadb/core/httpserver.nim missing wire import

docker-compose.override.yml

@@ -0,0 +1,16 @@
+# BaraDB — Docker Compose Override (автоматично зарежда се от docker compose)
+# Този файл се използва за development настройки когато използвате:
+#   docker compose up -d
+#
+# За production използвайте:
+#   docker compose -f docker-compose.prod.yml up -d
+
+services:
+  baradb:
+    # Development настройки
+    environment:
+      - BARADB_LOG_LEVEL=debug
+
+    # Монтираме изходния код за development (ако работите върху кода)
+    # volumes:
+    #   - ./src:/app/src:ro