refactor:restructure project architecture

Reorganized application package structure to improve modularity and navigability. Moved files from `fbr` to `app` directory and renamed key modules to better reflect functionality, such as `celery_worker`. Additionally, updated all relevant imports and settings configurations to align with the new structure, including Django settings and task management.

fbr/celery_app.py

@@ -0,0 +1,24 @@
+# isort:skip_file
+# flake8: noqa
+
+import os
+
+from celery import Celery
+from celery.schedules import crontab
+
+os.environ.setdefault("DJANGO_SETTINGS_MODULE", "fbr.settings")
+
+from dbt_copilot_python.celery_health_check import healthcheck
+
+celery_app = Celery("fbr_celery")
+celery_app.config_from_object("django.conf:settings", namespace="CELERY")
+celery_app.autodiscover_tasks()
+
+celery_app = healthcheck.setup(celery_app)
+
+celery_app.conf.beat_schedule = {
+    "schedule-fbr-cache-task": {
+        "task": "celery_worker.tasks.rebuild_cache",
+        "schedule": crontab(hour="1", minute="0"),  # Runs daily at 1:00 AM
+    },
+}