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/slm_dashboard.py

@@ -5,7 +5,6 @@ Provides API endpoints for the Sound Level Meters dashboard page.
 """
 
 from fastapi import APIRouter, Request, Depends, Query
-from fastapi.templating import Jinja2Templates
 from fastapi.responses import HTMLResponse
 from sqlalchemy.orm import Session
 from sqlalchemy import func
@@ -18,11 +17,11 @@ import os
 from backend.database import get_db
 from backend.models import RosterUnit
 from backend.routers.roster_edit import sync_slm_to_slmm_cache
+from backend.templates_config import templates
 
 logger = logging.getLogger(__name__)
 
 router = APIRouter(prefix="/api/slm-dashboard", tags=["slm-dashboard"])
-templates = Jinja2Templates(directory="templates")
 
 # SLMM backend URL - configurable via environment variable
 SLMM_BASE_URL = os.getenv("SLMM_BASE_URL", "http://localhost:8100")