fix: container permissions and volume setup

Problems fixed:
- archivum user (UID 1000) could not write to bind-mounted /config or /data
  because Docker (especially on Windows/WSL2) creates volumes owned by root
- /data/wiki and /data/db subdirectories were never created, causing
  "no such file or directory" when the app tried to write files

Changes:
- docker/entrypoint.sh: runs as root, creates /config /data/wiki /data/db,
  chowns them to PUID:PGID, then drops privileges via su-exec
- Dockerfile: install su-exec + git, copy entrypoint, remove build-time
  USER directive (privilege drop happens at runtime via entrypoint)
- docker-compose.yml: switch local dev to named volumes so Docker manages
  ownership automatically (avoids Windows/WSL2 bind-mount permission issues);
  add TZ env var; explicit comments on how to switch to bind mounts

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docker/docker-compose.yml

@@ -8,10 +8,28 @@ services:
     restart: unless-stopped
     ports:
       - "8080:4000"
-    volumes:
-      - ${DOCKER_PATH:-./data}/config:/config
-      - ${DOCKER_PATH:-./data}/data:/data
+
     environment:
+      # Points to the config directory inside the container.
       DOCKER_PATH: /config
+      UI_DIR: /srv/archivum/ui
+      # Set to match the owner of the host directories (run `id` to check).
       PUID: ${PUID:-1000}
       PGID: ${PGID:-1000}
+      TZ: ${TZ:-Europe/Stockholm}
+
+    volumes:
+      # Configuration (config.json written here by Setup Wizard).
+      - archivum-config:/config
+      # All data: wiki files live in /data/wiki, SQLite db in /data/db.
+      # Using named volumes for local dev avoids Windows/WSL2 permission issues.
+      - archivum-data:/data
+
+# Named volumes let Docker manage ownership automatically.
+# Replace with bind mounts if you need direct host access:
+#   - ./local/config:/config
+#   - ./local/data:/data
+# (and make sure the host directories are owned by PUID:PGID)
+volumes:
+  archivum-config:
+  archivum-data: