Add Docker support and improve Dockerfile configuration

- Added `DOCKER.md` documentation to guide users on using Docker with the project.
- Migrated Dockerfile to use `oven/bun:1-alpine` for performance improvements.
- Refined build process and permissions in the container for better compatibility.
- Excluded `.idea/` files in `.gitignore`.
- Enhanced `.npmignore` to clean redundant blank lines.

DOCKER.md

@@ -0,0 +1,76 @@
+# Docker
+
+This project ships with a `Dockerfile` for building and running 9Router in a container.
+
+## Build image
+
+```bash
+docker build -t 9router .
+```
+
+## Start container
+
+```bash
+docker run --rm \
+  -p 20128:20128 \
+  -v "$HOME/.9router:/app/data" \
+  --name 9router \
+  9router
+```
+
+The app listens on port `20128` in the container.
+
+## What the volume does
+
+```bash
+-v "$HOME/.9router:/app/data"
+```
+
+This keeps your data outside the container so it survives restarts and image rebuilds.
+
+## Stop container
+
+```bash
+docker stop 9router
+```
+
+## Run in background
+
+```bash
+docker run -d \
+  -p 20128:20128 \
+  -v "$HOME/.9router:/app/data" \
+  --name 9router \
+  9router
+```
+
+## View logs
+
+```bash
+docker logs -f 9router
+```
+
+## Optional environment variables
+
+You can override runtime env vars with `-e`.
+
+Example:
+
+```bash
+docker run --rm \
+  -p 20128:20128 \
+  -v "$HOME/.9router:/app/data" \
+  -e PORT=20128 \
+  -e HOSTNAME=0.0.0.0 \
+  -e DEBUG=true \
+  --name 9router \
+  9router
+```
+
+## Rebuild after code changes
+
+```bash
+docker build -t 9router .
+```
+
+Then restart the container.