Add dev init script with auto-created admin user (admin/admin) on first boot

dev/init.sh

@@ -0,0 +1,35 @@
+#!/bin/bash
+# Mattermost init script — creates admin user on first boot.
+# This is mounted into the container and replaces the default command.
+
+set -e
+
+# Start Mattermost server in the background.
+/entrypoint.sh mattermost server &
+MM_PID=$!
+
+# Wait for the server to be ready.
+echo "init: waiting for Mattermost to start..."
+for i in $(seq 1 30); do
+    if curl -sf http://localhost:8065/api/v4/system/ping > /dev/null 2>&1; then
+        echo "init: Mattermost is ready"
+        break
+    fi
+    if [ "$i" = "30" ]; then
+        echo "init: Mattermost failed to start within 60s"
+        exit 1
+    fi
+    sleep 2
+done
+
+# Create admin user (idempotent — ignores if already exists).
+echo "init: creating admin user..."
+/mattermost/bin/mattermost user create \
+    --email admin@example.com \
+    --username admin \
+    --password admin \
+    --system_admin 2>/dev/null && echo "init: admin user created" \
+    || echo "init: admin user already exists (or creation skipped)"
+
+# Bring Mattermost to the foreground.
+wait $MM_PID