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>

docker-compose.yml

@@ -1,28 +1,34 @@
+# Every host-specific value comes from .env (see .env.example), so the
+# stack can be built and kept in sync by Arcane (or any Compose host)
+# without editing this file. Defaults below apply when a variable is unset.
 services:
   playlink:
-    build: .
-    image: playlink:latest
-    container_name: playlink
+    build:
+      context: .
+      args:
+        VERSION: ${PLAYLINK_VERSION:-dev}
+    image: ${PLAYLINK_IMAGE:-playlink:latest}
+    container_name: ${PLAYLINK_CONTAINER_NAME:-playlink}
     # Run as the user that owns your music (Unraid: nobody:users = 99:100).
-    user: "99:100"
+    user: "${PUID:-99}:${PGID:-100}"
     ports:
-      - "7480:7480"
+      - "${PLAYLINK_PORT:-7480}:7480"
     environment:
-      - TZ=America/Los_Angeles
-      - PLAYLINK_ALLOWED_ROOTS=/data
-      # Set to true when serving over HTTPS (e.g. behind a reverse proxy).
-      - PLAYLINK_SECURE_COOKIES=false
+      TZ: ${TZ:-America/Los_Angeles}
+      PLAYLINK_ALLOWED_ROOTS: ${PLAYLINK_ALLOWED_ROOTS:-/data}
+      PLAYLINK_SECURE_COOKIES: ${PLAYLINK_SECURE_COOKIES:-false}
+      PLAYLINK_LOG_LEVEL: ${PLAYLINK_LOG_LEVEL:-info}
     volumes:
-      - /mnt/user/Aqua/playlink:/config
-      # IMPORTANT: mount ONE folder that contains BOTH libraries. Hardlinks
+      - ${PLAYLINK_CONFIG_PATH:-/mnt/user/Aqua/playlink}:/config
+      # IMPORTANT: ONE folder that contains BOTH libraries. Hardlinks
       # cannot cross Docker bind mounts, even on the same disk.
-      #   master  (Albums)  -> /data/Music/Albums
-      #   slave (Singles) -> /data/Music/Instances/cdnutter/Singles
-      - /mnt/user/Sapphire:/data
-    restart: unless-stopped
+      - ${PLAYLINK_DATA_PATH:-/mnt/user/Sapphire}:/data
+    restart: ${PLAYLINK_RESTART:-unless-stopped}
     networks:
-      - chromanet
+      - playlink
 
 networks:
-  chromanet:
+  playlink:
+    # An existing Docker network (e.g. the one your reverse proxy uses).
+    name: ${PLAYLINK_NETWORK:-chromanet}
     external: true