feat: complete LOW priority code quality improvements

Backend:
- LOW-002: Add Query validation with max page size limits (100)
- LOW-003: Replace magic strings with TaskStatus.is_done flag
- LOW-004: Add 'creation' trigger type validation
- Add action_executor.py with UpdateFieldAction and AutoAssignAction

Frontend:
- LOW-005: Replace TypeScript 'any' with 'unknown' + type guards
- LOW-006: Add ConfirmModal component with A11Y support
- LOW-007: Add ToastContext for user feedback notifications
- LOW-009: Add Skeleton components (17 loading states replaced)
- LOW-010: Setup Vitest with 21 tests for ConfirmModal and Skeleton

Components updated:
- App.tsx, ProtectedRoute.tsx, Spaces.tsx, Projects.tsx, Tasks.tsx
- ProjectSettings.tsx, AuditPage.tsx, WorkloadPage.tsx, ProjectHealthPage.tsx
- Comments.tsx, AttachmentList.tsx, TriggerList.tsx, TaskDetailModal.tsx
- NotificationBell.tsx, BlockerDialog.tsx, CalendarView.tsx, WorkloadUserDetail.tsx

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/app/api/triggers/router.py

@@ -1,5 +1,5 @@
 import uuid
-from fastapi import APIRouter, Depends, HTTPException, status
+from fastapi import APIRouter, Depends, HTTPException, status, Query
 from sqlalchemy.orm import Session
 from typing import Optional
 
@@ -11,6 +11,8 @@ from app.schemas.trigger import (
 )
 from app.middleware.auth import get_current_user, check_project_access, check_project_edit_access
 from app.services.trigger_scheduler import TriggerSchedulerService
+from app.services.trigger_service import TriggerService
+from app.services.action_executor import ActionValidationError
 
 router = APIRouter(tags=["triggers"])
 
@@ -60,10 +62,11 @@ async def create_trigger(
         )
 
     # Validate trigger type
-    if trigger_data.trigger_type not in ["field_change", "schedule"]:
+    valid_trigger_types = ["field_change", "schedule", "creation"]
+    if trigger_data.trigger_type not in valid_trigger_types:
         raise HTTPException(
             status_code=status.HTTP_400_BAD_REQUEST,
-            detail="Invalid trigger type. Must be 'field_change' or 'schedule'",
+            detail=f"Invalid trigger type. Must be one of: {', '.join(valid_trigger_types)}",
         )
 
     # Validate conditions based on trigger type
@@ -111,6 +114,16 @@ async def create_trigger(
                     detail=error_msg or "Invalid cron expression",
                 )
 
+    # Validate actions configuration (FEAT-014, FEAT-015)
+    try:
+        actions_dicts = [a.model_dump(exclude_none=True) for a in trigger_data.actions]
+        TriggerService.validate_actions(actions_dicts, db)
+    except ActionValidationError as e:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=str(e),
+        )
+
     # Create trigger
     trigger = Trigger(
         id=str(uuid.uuid4()),
@@ -119,7 +132,7 @@ async def create_trigger(
         description=trigger_data.description,
         trigger_type=trigger_data.trigger_type,
         conditions=trigger_data.conditions.model_dump(),
-        actions=[a.model_dump() for a in trigger_data.actions],
+        actions=[a.model_dump(exclude_none=True) for a in trigger_data.actions],
         is_active=trigger_data.is_active,
         created_by=current_user.id,
     )
@@ -239,7 +252,16 @@ async def update_trigger(
                     )
         trigger.conditions = trigger_data.conditions.model_dump(exclude_none=True)
     if trigger_data.actions is not None:
-        trigger.actions = [a.model_dump() for a in trigger_data.actions]
+        # Validate actions configuration (FEAT-014, FEAT-015)
+        try:
+            actions_dicts = [a.model_dump(exclude_none=True) for a in trigger_data.actions]
+            TriggerService.validate_actions(actions_dicts, db)
+        except ActionValidationError as e:
+            raise HTTPException(
+                status_code=status.HTTP_400_BAD_REQUEST,
+                detail=str(e),
+            )
+        trigger.actions = [a.model_dump(exclude_none=True) for a in trigger_data.actions]
     if trigger_data.is_active is not None:
         trigger.is_active = trigger_data.is_active
 
@@ -278,8 +300,8 @@ async def delete_trigger(
 @router.get("/api/triggers/{trigger_id}/logs", response_model=TriggerLogListResponse)
 async def list_trigger_logs(
     trigger_id: str,
-    limit: int = 50,
-    offset: int = 0,
+    limit: int = Query(50, ge=1, le=200, description="Number of logs to return"),
+    offset: int = Query(0, ge=0, description="Number of logs to skip"),
     db: Session = Depends(get_db),
     current_user: User = Depends(get_current_user),
 ):