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/templates_config.py

@@ -0,0 +1,39 @@
+"""
+Shared Jinja2 templates configuration.
+
+All routers should import `templates` from this module to get consistent
+filter and global function registration.
+"""
+
+from fastapi.templating import Jinja2Templates
+
+# Import timezone utilities
+from backend.utils.timezone import (
+    format_local_datetime, format_local_time,
+    get_user_timezone, get_timezone_abbreviation
+)
+
+
+def jinja_local_datetime(dt, fmt="%Y-%m-%d %H:%M"):
+    """Jinja filter to convert UTC datetime to local timezone."""
+    return format_local_datetime(dt, fmt)
+
+
+def jinja_local_time(dt):
+    """Jinja filter to format time in local timezone."""
+    return format_local_time(dt)
+
+
+def jinja_timezone_abbr():
+    """Jinja global to get current timezone abbreviation."""
+    return get_timezone_abbreviation()
+
+
+# Create templates instance
+templates = Jinja2Templates(directory="templates")
+
+# Register Jinja filters and globals
+templates.env.filters["local_datetime"] = jinja_local_datetime
+templates.env.filters["local_time"] = jinja_local_time
+templates.env.globals["timezone_abbr"] = jinja_timezone_abbr
+templates.env.globals["get_user_timezone"] = get_user_timezone