refactor: enhance type hinting and casting for improved type safety across multiple files

app/models/activity.py

@@ -10,9 +10,11 @@ from pydantic import BaseModel, ConfigDict, Field
 from sqlalchemy import DateTime, ForeignKey, Integer, func, text
 from sqlalchemy import Enum as SqlEnum
 from sqlalchemy.dialects.postgresql import JSONB
+from sqlalchemy.engine import Dialect
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 from sqlalchemy.types import JSON as SA_JSON
 from sqlalchemy.types import TypeDecorator
+from sqlalchemy.sql.type_api import TypeEngine
 
 from app.models.base import Base, enum_values
 
@@ -31,7 +33,7 @@ class JSONBCompat(TypeDecorator):
     impl = JSONB
     cache_ok = True
 
-    def load_dialect_impl(self, dialect):  # type: ignore[override]
+    def load_dialect_impl(self, dialect: Dialect) -> TypeEngine[Any]:
         if dialect.name == "sqlite":
             from sqlalchemy.dialects.sqlite import JSON as SQLITE_JSON  # local import