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/utils/timezone.py

@@ -0,0 +1,173 @@
+"""
+Timezone utilities for Terra-View.
+
+Provides consistent timezone handling throughout the application.
+All database times are stored in UTC; this module converts for display.
+"""
+
+from datetime import datetime
+from zoneinfo import ZoneInfo
+from typing import Optional
+
+from backend.database import SessionLocal
+from backend.models import UserPreferences
+
+
+# Default timezone if none set
+DEFAULT_TIMEZONE = "America/New_York"
+
+
+def get_user_timezone() -> str:
+    """
+    Get the user's configured timezone from preferences.
+
+    Returns:
+        Timezone string (e.g., "America/New_York")
+    """
+    db = SessionLocal()
+    try:
+        prefs = db.query(UserPreferences).filter_by(id=1).first()
+        if prefs and prefs.timezone:
+            return prefs.timezone
+        return DEFAULT_TIMEZONE
+    finally:
+        db.close()
+
+
+def get_timezone_info(tz_name: str = None) -> ZoneInfo:
+    """
+    Get ZoneInfo object for the specified or user's timezone.
+
+    Args:
+        tz_name: Timezone name, or None to use user preference
+
+    Returns:
+        ZoneInfo object
+    """
+    if tz_name is None:
+        tz_name = get_user_timezone()
+    try:
+        return ZoneInfo(tz_name)
+    except Exception:
+        return ZoneInfo(DEFAULT_TIMEZONE)
+
+
+def utc_to_local(dt: datetime, tz_name: str = None) -> datetime:
+    """
+    Convert a UTC datetime to local timezone.
+
+    Args:
+        dt: Datetime in UTC (naive or aware)
+        tz_name: Target timezone, or None to use user preference
+
+    Returns:
+        Datetime in local timezone
+    """
+    if dt is None:
+        return None
+
+    tz = get_timezone_info(tz_name)
+
+    # Assume naive datetime is UTC
+    if dt.tzinfo is None:
+        dt = dt.replace(tzinfo=ZoneInfo("UTC"))
+
+    return dt.astimezone(tz)
+
+
+def local_to_utc(dt: datetime, tz_name: str = None) -> datetime:
+    """
+    Convert a local datetime to UTC.
+
+    Args:
+        dt: Datetime in local timezone (naive or aware)
+        tz_name: Source timezone, or None to use user preference
+
+    Returns:
+        Datetime in UTC (naive, for database storage)
+    """
+    if dt is None:
+        return None
+
+    tz = get_timezone_info(tz_name)
+
+    # Assume naive datetime is in local timezone
+    if dt.tzinfo is None:
+        dt = dt.replace(tzinfo=tz)
+
+    # Convert to UTC and strip tzinfo for database storage
+    return dt.astimezone(ZoneInfo("UTC")).replace(tzinfo=None)
+
+
+def format_local_datetime(dt: datetime, fmt: str = "%Y-%m-%d %H:%M", tz_name: str = None) -> str:
+    """
+    Format a UTC datetime as local time string.
+
+    Args:
+        dt: Datetime in UTC
+        fmt: strftime format string
+        tz_name: Target timezone, or None to use user preference
+
+    Returns:
+        Formatted datetime string in local time
+    """
+    if dt is None:
+        return "N/A"
+
+    local_dt = utc_to_local(dt, tz_name)
+    return local_dt.strftime(fmt)
+
+
+def format_local_time(dt: datetime, tz_name: str = None) -> str:
+    """
+    Format a UTC datetime as local time (HH:MM format).
+
+    Args:
+        dt: Datetime in UTC
+        tz_name: Target timezone
+
+    Returns:
+        Time string in HH:MM format
+    """
+    return format_local_datetime(dt, "%H:%M", tz_name)
+
+
+def format_local_date(dt: datetime, tz_name: str = None) -> str:
+    """
+    Format a UTC datetime as local date (YYYY-MM-DD format).
+
+    Args:
+        dt: Datetime in UTC
+        tz_name: Target timezone
+
+    Returns:
+        Date string
+    """
+    return format_local_datetime(dt, "%Y-%m-%d", tz_name)
+
+
+def get_timezone_abbreviation(tz_name: str = None) -> str:
+    """
+    Get the abbreviation for a timezone (e.g., EST, EDT, PST).
+
+    Args:
+        tz_name: Timezone name, or None to use user preference
+
+    Returns:
+        Timezone abbreviation
+    """
+    tz = get_timezone_info(tz_name)
+    now = datetime.now(tz)
+    return now.strftime("%Z")
+
+
+# Common US timezone choices for settings dropdown
+TIMEZONE_CHOICES = [
+    ("America/New_York", "Eastern Time (ET)"),
+    ("America/Chicago", "Central Time (CT)"),
+    ("America/Denver", "Mountain Time (MT)"),
+    ("America/Los_Angeles", "Pacific Time (PT)"),
+    ("America/Anchorage", "Alaska Time (AKT)"),
+    ("Pacific/Honolulu", "Hawaii Time (HT)"),
+    ("UTC", "UTC"),
+]