feat: complete dev_tools module self-containment

Migrate dev_tools module to self-contained structure:

- routes/api/ - API endpoints
- models/architecture_scan.py - Architecture scan models
- models/test_run.py - Test run models
- schemas/ - Pydantic schemas
- services/ - Business logic services
- tasks/ - Celery background tasks
- exceptions.py - Module exceptions

Updated definition.py with self-contained paths.

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

app/modules/dev_tools/tasks/test_runner.py

@@ -0,0 +1,85 @@
+# app/modules/dev_tools/tasks/test_runner.py
+"""
+Celery tasks for test execution.
+
+Wraps the existing execute_test_run function for Celery execution.
+This is the canonical location - task is re-exported from the legacy location
+for backward compatibility.
+"""
+
+import logging
+
+from app.core.celery_config import celery_app
+from app.services.test_runner_service import test_runner_service
+from app.tasks.celery_tasks.base import DatabaseTask
+from app.modules.dev_tools.models import TestRun
+
+logger = logging.getLogger(__name__)
+
+
+@celery_app.task(
+    bind=True,
+    base=DatabaseTask,
+    name="app.modules.dev_tools.tasks.test_runner.execute_test_run",
+    max_retries=1,
+    time_limit=3600,  # 1 hour hard limit
+    soft_time_limit=3300,  # 55 minutes soft limit
+)
+def execute_test_run(
+    self,
+    run_id: int,
+    test_path: str = "tests",
+    extra_args: list[str] | None = None,
+):
+    """
+    Celery task to execute pytest tests.
+
+    Args:
+        run_id: ID of the TestRun record
+        test_path: Path to tests (relative to project root)
+        extra_args: Additional pytest arguments
+
+    Returns:
+        dict: Test run results summary
+    """
+    with self.get_db() as db:
+        # Get the test run record
+        test_run = db.query(TestRun).filter(TestRun.id == run_id).first()
+        if not test_run:
+            logger.error(f"Test run {run_id} not found")
+            return {"error": f"Test run {run_id} not found"}
+
+        # Store Celery task ID
+        test_run.celery_task_id = self.request.id
+        db.commit()
+
+        try:
+            logger.info(f"Starting test execution: Run {run_id}, Path: {test_path}")
+
+            # Execute the tests
+            test_runner_service._execute_tests(db, test_run, test_path, extra_args)
+            db.commit()
+
+            logger.info(
+                f"Test run {run_id} completed: "
+                f"status={test_run.status}, passed={test_run.passed}, "
+                f"failed={test_run.failed}, duration={test_run.duration_seconds:.1f}s"
+            )
+
+            return {
+                "run_id": run_id,
+                "status": test_run.status,
+                "total_tests": test_run.total_tests,
+                "passed": test_run.passed,
+                "failed": test_run.failed,
+                "errors": test_run.errors,
+                "skipped": test_run.skipped,
+                "coverage_percent": test_run.coverage_percent,
+                "duration_seconds": test_run.duration_seconds,
+            }
+
+        except Exception as e:
+            logger.error(f"Test run {run_id} failed: {e}", exc_info=True)
+            test_run.status = "error"
+            db.commit()
+            raise  # Re-raise for Celery