Build in-place for a Portainer git stack

No registry exists yet and there is no SSH onto Nox, so Portainer clones this
repo there and compose builds the image on the box. Adds build: . and moves the
default host port to 8086, which is free on Nox (808x is crowded).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GVbG48GAXfCZatcmX123Ra

docker-compose.yml

@@ -4,16 +4,19 @@
 # A variable set in Portainer's UI but absent from this file silently does
 # nothing — the trap that bit PLAYERMAP_SHOW_GMS on the Mythica stack.
 #
-# The image is built off-box and pushed/loaded onto Nox (§11.2). Pin a real
-# version tag; never deploy bare :latest.
+# Deployed as a Portainer *git* stack: Portainer clones this repo onto Nox and
+# `docker compose up` builds the image there, so no registry is needed. The
+# image: tag still pins a real version so a redeploy replaces it predictably
+# rather than reusing a stale :latest.
 
 services:
   mediashelf:
     image: ${MEDIASHELF_IMAGE:-mediashelf:0.1.0}
+    build: .
     container_name: mediashelf
     restart: unless-stopped
     ports:
-      - "${MEDIASHELF_PORT:-8085}:8080"
+      - "${MEDIASHELF_PORT:-8086}:8080"
     volumes:
       - mediashelf_data:/data
     environment: