fix(admin-invites): left-align create card conditional fields, convert local datetime to UTC on save

app/routers/web.py

@@ -47,6 +47,14 @@ def _to_local(dt: datetime) -> datetime:
     return dt.astimezone(_CST)
 
 
+def _to_utc(dt_str: str) -> datetime:
+    """Parse local datetime-local string and convert to UTC."""
+    dt = datetime.fromisoformat(dt_str)
+    if dt.tzinfo is None:
+        dt = dt.replace(tzinfo=_CST)
+    return dt.astimezone(timezone.utc).replace(tzinfo=None)
+
+
 templates.env.filters["to_local"] = _to_local
 
 
@@ -218,7 +226,7 @@ def admin_add_invite(
     if limit_type == "uses" and max_uses:
         m_uses = max_uses
     elif limit_type == "expires" and expires_at:
-        exp_at = datetime.fromisoformat(expires_at)
+        exp_at = _to_utc(expires_at)
     new_code = InviteCode(
         code=code, max_uses=m_uses, expires_at=exp_at,
         use_count=0, created_by=user.id,
@@ -251,7 +259,7 @@ def admin_edit_invite(
         code_obj.max_uses = max_uses
         code_obj.expires_at = None
     elif limit_type == "expires" and expires_at:
-        code_obj.expires_at = datetime.fromisoformat(expires_at)
+        code_obj.expires_at = _to_utc(expires_at)
         code_obj.max_uses = None
     else:
         code_obj.max_uses = None