chore(lint): apply ruff --fix (4443 auto-fixes)

Auto-fixed categories:
- F401: unused imports removed
- I001: import blocks sorted
- W293: trailing whitespace stripped
- UP035: deprecated typing imports replaced
- SIM: simplify suggestions applied
- ARG: unused args prefixed with underscore
- T201: print statements removed
- F841: unused variables removed
- RUF059: unpacked variables prefixed

Remaining ~1500 unfixable errors (C901, B904, N806, E402) require manual work.

Backend smoke tests: 13/13 passed.

backend/src/services/reports/normalizer.py

@@ -11,7 +11,7 @@
 # @SIDE_EFFECT: Read-only database operations
 
 from datetime import datetime
-from typing import Any, Dict, Optional
+from typing import Any
 
 from ...core.logger import belief_scope
 from ...core.task_manager.models import Task, TaskStatus
@@ -62,7 +62,7 @@ def build_summary(task: Task, report_status: ReportStatus) -> str:
 # @BRIEF Extract normalized error context and next actions for failed/partial reports.
 # @PRE: task is a valid Task object.
 # @POST: Returns ErrorContext for failed/partial when context exists; otherwise None.
-def extract_error_context(task: Task, report_status: ReportStatus) -> Optional[ErrorContext]:
+def extract_error_context(task: Task, report_status: ReportStatus) -> ErrorContext | None:
     with belief_scope("extract_error_context"):
         if report_status not in {ReportStatus.FAILED, ReportStatus.PARTIAL}:
             return None
@@ -128,7 +128,7 @@ def normalize_task_report(task: Task) -> TaskReport:
         if not updated_at:
             updated_at = started_at or datetime.utcnow()
 
-        details: Dict[str, Any] = {
+        details: dict[str, Any] = {
             "profile": {
                 "display_label": profile.get("display_label"),
                 "visual_variant": profile.get("visual_variant"),
@@ -138,7 +138,7 @@ def normalize_task_report(task: Task) -> TaskReport:
             "result": task.result if task.result is not None else {"note": "Not provided"},
         }
 
-        source_ref: Dict[str, Any] = {}
+        source_ref: dict[str, Any] = {}
         if isinstance(task.params, dict):
             for key in ("environment_id", "source_env_id", "target_env_id", "dashboard_id", "dataset_id", "resource_id"):
                 if key in task.params:
@@ -158,4 +158,4 @@ def normalize_task_report(task: Task) -> TaskReport:
         )
 # #endregion normalize_task_report
 
-# #endregion normalizer
+# #endregion normalizer