tuning ui and adding adaptive themeing to extension

backend/app/models/base.py

@@ -1,6 +1,6 @@
 """SQLAlchemy base model."""
 
-from datetime import datetime
+from datetime import datetime, timezone
 from sqlalchemy import func
 from sqlalchemy.orm import DeclarativeBase, Mapped, mapped_column
 
@@ -10,8 +10,29 @@ class Base(DeclarativeBase):
     pass
 
 
-class TimestampMixin:
-    """Mixin for created_at and updated_at timestamps."""
+def utcnow():
+    """Return current UTC time as timezone-aware datetime."""
+    return datetime.now(timezone.utc)
 
-    created_at: Mapped[datetime] = mapped_column(default=func.now())
-    updated_at: Mapped[datetime] = mapped_column(default=func.now(), onupdate=func.now())
+
+def format_datetime(dt):
+    """Format datetime as ISO string with UTC marker for API responses.
+
+    If the datetime is naive (no timezone), assumes UTC and appends Z.
+    This ensures JavaScript Date() correctly interprets the timezone.
+    """
+    if not dt:
+        return None
+    # If naive (no timezone), assume UTC and append Z
+    if dt.tzinfo is None:
+        return dt.isoformat() + "Z"
+    return dt.isoformat()
+
+
+class TimestampMixin:
+    """Mixin for created_at and updated_at timestamps.
+
+    Uses UTC timestamps for consistency. Frontend should convert to local time.
+    """
+    created_at: Mapped[datetime] = mapped_column(default=utcnow)
+    updated_at: Mapped[datetime] = mapped_column(default=utcnow, onupdate=utcnow)