Refactor EPG scheduling: replace CRON_SCHEDULE with GRAB_INTERVAL_HOURS for improved interval-based grabbing and add lock mechanism to prevent concurrent executions.

Dockers/iptv-epg/Dockerfile

@@ -1,7 +1,7 @@
 FROM node:20-alpine
 
 # Install required packages
-RUN apk add --no-cache git curl unzip coreutils dcron
+RUN apk add --no-cache git curl unzip coreutils
 
 # Set working directory
 WORKDIR /app
@@ -22,7 +22,7 @@ RUN chmod +x /app/entrypoint.sh
 EXPOSE 3000
 
 # Set environment variables with defaults
-ENV CRON_SCHEDULE="0 0,12 * * *" \
+ENV GRAB_INTERVAL_HOURS=12 \
     SITES="" \
     MAX_CONNECTIONS=10 \
     DAYS="" \