feat: Refactor template handling, improve scheduler functions, and add timezone utilities

- Moved Jinja2 template setup to a shared configuration file (templates_config.py) for consistent usage across routers.
- Introduced timezone utilities in a new module (timezone.py) to handle UTC to local time conversions and formatting.
- Updated all relevant routers to use the new shared template configuration and timezone filters.
- Enhanced templates to utilize local time formatting for various datetime fields, improving user experience with timezone awareness.

backend/routers/alerts.py

@@ -5,7 +5,6 @@ API endpoints for managing in-app alerts.
 """
 
 from fastapi import APIRouter, Request, Depends, HTTPException, Query
-from fastapi.templating import Jinja2Templates
 from fastapi.responses import HTMLResponse, JSONResponse
 from sqlalchemy.orm import Session
 from typing import Optional
@@ -14,9 +13,9 @@ from datetime import datetime, timedelta
 from backend.database import get_db
 from backend.models import Alert, RosterUnit
 from backend.services.alert_service import get_alert_service
+from backend.templates_config import templates
 
 router = APIRouter(prefix="/api/alerts", tags=["alerts"])
-templates = Jinja2Templates(directory="templates")
 
 
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