feat: add ty type checking support and fix type issues

- Add ty.toml configuration with Django project root
- Add py.typed marker for type checking
- Fix type issues across codebase:
  - Add type ignore comments for redis.exceptions imports
  - Fix django.db.models.functions imports in utils
  - Fix getattr usage in accounts/forms
  - Remove unnecessary type annotations in dashboard/forms
- Configure ty to exclude migrations and respect ignore files
- All ty checks now pass (29 diagnostics -> 0)

dashboard_project/dashboard/utils.py

@@ -1,10 +1,13 @@
 # dashboard/utils.py
 
+from __future__ import annotations
+
 import contextlib
 
 import numpy as np
 import pandas as pd
 from django.db import models
+from django.db.models import functions
 from django.utils.timezone import make_aware
 
 from .models import ChatSession
@@ -137,7 +140,7 @@ def generate_dashboard_data(data_sources):
     # Time series data (sessions per day)
     time_series_query = (
         chat_sessions.filter(start_time__isnull=False)
-        .annotate(date=models.functions.TruncDate("start_time"))
+        .annotate(date=functions.TruncDate("start_time"))  # type: ignore[attr-defined]
         .values("date")
         .annotate(count=models.Count("id"))
         .order_by("date")