Refactor scheduled task repository and schemas for improved type hints and consistency

- Updated type hints from List/Optional to list/None for better readability and consistency across the codebase.
- Refactored import statements for better organization and clarity.
- Enhanced the ScheduledTaskBase schema to use modern type hints.
- Cleaned up unnecessary comments and whitespace in various files.
- Improved error handling and logging in task execution handlers.
- Updated test cases to reflect changes in type hints and ensure compatibility with the new structure.

app/models/scheduled_task.py

@@ -1,11 +1,10 @@
 """Scheduled task model for flexible task scheduling with timezone support."""
 
-import uuid
 from datetime import datetime
 from enum import Enum
-from typing import Any, Optional
+from typing import Any
 
-from sqlmodel import JSON, Column, Field, SQLModel
+from sqlmodel import JSON, Column, Field
 
 from app.models.base import BaseModel
 
@@ -57,11 +56,11 @@ class ScheduledTask(BaseModel, table=True):
         description="Timezone for scheduling (e.g., 'America/New_York', 'Europe/Paris')",
     )
     recurrence_type: RecurrenceType = Field(default=RecurrenceType.NONE)
-    cron_expression: Optional[str] = Field(
+    cron_expression: str | None = Field(
         default=None,
         description="Cron expression for custom recurrence (when recurrence_type is CRON)",
     )
-    recurrence_count: Optional[int] = Field(
+    recurrence_count: int | None = Field(
         default=None,
         description="Number of times to repeat (None for infinite)",
     )
@@ -75,29 +74,29 @@ class ScheduledTask(BaseModel, table=True):
     )
 
     # User association (None for system tasks)
-    user_id: Optional[int] = Field(
+    user_id: int | None = Field(
         default=None,
         foreign_key="user.id",
         description="User who created the task (None for system tasks)",
     )
 
     # Execution tracking
-    last_executed_at: Optional[datetime] = Field(
+    last_executed_at: datetime | None = Field(
         default=None,
         description="When the task was last executed (UTC)",
     )
-    next_execution_at: Optional[datetime] = Field(
+    next_execution_at: datetime | None = Field(
         default=None,
         description="When the task should be executed next (UTC, for recurring tasks)",
     )
-    error_message: Optional[str] = Field(
+    error_message: str | None = Field(
         default=None,
         description="Error message if execution failed",
     )
 
     # Task lifecycle
     is_active: bool = Field(default=True, description="Whether the task is active")
-    expires_at: Optional[datetime] = Field(
+    expires_at: datetime | None = Field(
         default=None,
         description="When the task expires (UTC, optional)",
     )
@@ -122,4 +121,4 @@ class ScheduledTask(BaseModel, table=True):
 
     def is_system_task(self) -> bool:
         """Check if this is a system task (no user association)."""
-        return self.user_id is None
+        return self.user_id is None