docs: add QUEUE_DB_PATH context and create .env.example

Added QUEUE_DB_PATH documentation to README and created .env.example with queue config variables. Job queue types remain in utils due to import cycle.

Author: Hell1213

backend/.env.example

@@ -0,0 +1,21 @@
+# Google OAuth Configuration
+CLIENT_ID="your_client_id_here"
+CLIENT_SEC="your_client_secret_here"
+REDIRECT_URL_DEV="http://localhost:8000/auth/callback"
+SESSION_KEY="your_session_key_here"
+
+# Frontend Configuration
+# For Docker:
+FRONTEND_ORIGIN_DEV="http://localhost"
+CONTAINER_ORIGIN="http://YOUR_CONTAINER_NAME:8080/"
+# For npm run dev:
+# FRONTEND_ORIGIN_DEV="http://localhost:5173"
+# CONTAINER_ORIGIN="http://localhost:8080/"
+
+# Optional: Custom Backend Port
+# CCSYNC_PORT="8081"
+
+# Job Queue Configuration
+CLEANUP_CRON_SCHEDULE="0 0 * * *"    # Daily at midnight
+CLEANUP_RETENTION_DAYS="7"           # Keep logs for 7 days
+QUEUE_DB_PATH="/app/data/queue.db"   # Queue database location

backend/README.md

@@ -82,7 +82,7 @@ The job queue system uses the following environment variables:
 
 ### Database Location
 
-The queue database is stored at `/app/data/queue.db` inside the container, which is mounted to `./backend/data/queue.db` on the host system via Docker volume.
+The queue database is stored at `/app/data/queue.db` inside the container, which is mounted to `./backend/data/queue.db` on the host system via Docker volume. The `QUEUE_DB_PATH` environment variable can be used to customize this location if needed.
 
 - Run the application:
 

backend/utils/persistent_queue.go

@@ -10,6 +10,8 @@ import (
 	"go.etcd.io/bbolt"
 )
 
+// IMP ==> JobState and PersistentJob remain in utils due to import cycle with models/logs.go
+
 type JobState string
 
 const (