Configure Docker Compose through .env for Arcane

docker-compose.yml now reads every host-specific value (paths, user,
port, network, time zone) from .env with the previous values as
defaults. .env.example documents them; .env stays out of Git.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -198,21 +198,29 @@ playlink is built so that no user data is ever lost, even if it crashes or loses
 
 ## Quick start (Docker / Unraid)
 
-```yaml
-services:
-  playlink:
-    build: .            # or your published image
-    container_name: playlink
-    user: "99:100"      # owner of your music files (Unraid nobody:users)
-    ports: ["7480:7480"]
-    environment:
-      - PLAYLINK_ALLOWED_ROOTS=/data
-    volumes:
-      - /mnt/user/appdata/playlink:/config
-      - /mnt/user/Sapphire/Media/Music:/data/Music   # ONE mount containing both libraries
-    restart: unless-stopped
+`docker-compose.yml` takes every host-specific value from a `.env` file next to it, so the compose file itself never needs editing. That
+suits [Arcane](https://github.com/ofkm/arcane): point a project's Git Sync at this repository and set the values in Arcane's `.env` editor;
+Arcane builds the image from the `Dockerfile`. With plain Compose:
+
+```sh
+cp .env.example .env    # then edit it
+docker compose up -d --build
 ```
 
+The main settings (all listed with defaults in `.env.example`):
+
+| Variable | Default | Meaning |
+|---|---|---|
+| `PLAYLINK_DATA_PATH` | `/mnt/user/Sapphire` | Host folder containing **both** libraries, mounted at `/data`. |
+| `PLAYLINK_CONFIG_PATH` | `/mnt/user/Aqua/playlink` | Host folder for the database and backups, mounted at `/config`. |
+| `PUID` / `PGID` | `99` / `100` | User and group that own your music (Unraid `nobody:users`). |
+| `PLAYLINK_PORT` | `7480` | Host port of the web UI. |
+| `PLAYLINK_NETWORK` | `chromanet` | Existing Docker network to join. |
+| `TZ` | `America/Los_Angeles` | Time zone for logs and backup schedules. |
+| `PLAYLINK_SECURE_COOKIES` | `false` | `true` behind HTTPS. |
+
+`.env` is ignored by Git, so your settings stay local while the repository syncs.
+
 Then open `http://<server>:7480`, create your account, and add a pair:
 
 - Master: `/data/Music/Albums`