Add Docker-Compose setup with configurable local port via .env.

Document container startup and local port configuration in README, including a .env example for quick setup.

Made-with: Cursor

.env.example

@@ -0,0 +1 @@
+LOCAL_PORT=5000

README.md

@@ -14,6 +14,38 @@ pip install -r requirements.txt
 python app.py
 ```
 
+## Docker Compose
+
+Run the app with Docker Compose and configure the local host port via `.env`.
+
+1. Create a `.env` file in the project root (or copy `.env.example`):
+
+```bash
+# macOS / Linux
+cp .env.example .env
+
+# Windows (PowerShell)
+Copy-Item .env.example .env
+```
+
+2. Set the local host port in `.env`:
+
+```dotenv
+LOCAL_PORT=5000
+```
+
+3. Build and start the container:
+
+```bash
+docker compose up --build -d
+```
+
+4. Open the app in your browser:
+
+```text
+http://localhost:<LOCAL_PORT>
+```
+
 Visit [https://date.elpatron.me](https://date.elpatron.me) for the live demo.
 
 ## License

docker-compose.yml

@@ -0,0 +1,8 @@
+services:
+  datecalc:
+    build:
+      context: .
+      dockerfile: Dockerfile
+    ports:
+      - "${LOCAL_PORT:-5000}:5000"
+    restart: unless-stopped