docker (demo): fix starting + better UX:

- Use the new `wait_for_service` option to be sure that Prosody is launched.
- Use the new `init_script_path` option to initiate forums and bookmark a demo room.
- Activate MUC service.
- Change log formats to make them more readable.

docker/backend-dev-demo/scripts/init_script.sh

@@ -0,0 +1,17 @@
+#!/bin/bash
+
+SETUP_INDICATOR="/home/libervia/.local/share/libervia/setup_complete.flag"
+FORUMS_JSON_FILE="/home/libervia/forums.json"
+
+if [ ! -f "$SETUP_INDICATOR" ]; then
+    echo "First run detected. Setting up the environment and configuration."
+
+    libervia-cli profile modify -D -cp demo --pwd demo
+    libervia-cli forums set -p demo < $FORUMS_JSON_FILE
+    libervia-cli bookmarks add -pdemo -a demo@chat.server1.test
+
+    touch "$SETUP_INDICATOR"
+    echo "Initial setup complete."
+else
+    echo "Not the first run. Skipping setup."
+fi