feat: 内容数据迁移至数据库，合规审查全链路打通

- 文章 HTML 存储从文件系统迁移至 articles 表，删除 releases 目录
- 合规审查从 DB 读取 HTML，审查结果写回 DB，通过后自动推进至待发布
- 新增 todayCount 筛选按钮，与系统概览统计数据一致
- 全屏预览修复：提升 z-index 超过侧边栏，添加退出全屏/关闭按钮
- 统一 '优化' → '审查' 命名，消除前后端术语不一致
- 调度器创作完成后自动触发审查（生成 → 审查 → 待发布）
- 清理旧备份/调试文件、过期大纲和研究笔记

platform/backend/app/api/tasks.py

@@ -88,9 +88,9 @@ def start_task(
     if not task:
         raise HTTPException(status_code=404, detail="任务不存在")
 
-    from datetime import datetime
+    from datetime import datetime, timezone
     task.status = "running"
-    task.started_at = datetime.now()
+    task.started_at = datetime.now(timezone.utc)
     task.message = "任务已启动"
     task.progress = 0
     db.commit()
@@ -130,16 +130,17 @@ def complete_task(
     if not task:
         raise HTTPException(status_code=404, detail="任务不存在")
 
-    from datetime import datetime
+    from datetime import datetime, timezone
+    finished = datetime.now(timezone.utc)
     task.status = "completed"
-    task.finished_at = datetime.now()
+    task.finished_at = finished
     task.progress = 100
     if message:
         task.message = message
     if result_data:
         task.result_data = result_data
     if task.started_at:
-        task.duration = int((task.finished_at - task.started_at).total_seconds())
+        task.duration = int((finished - task.started_at).total_seconds())
     db.commit()
     db.refresh(task)
     return task
@@ -156,12 +157,13 @@ def fail_task(
     if not task:
         raise HTTPException(status_code=404, detail="任务不存在")
 
-    from datetime import datetime
+    from datetime import datetime, timezone
+    finished = datetime.now(timezone.utc)
     task.status = "failed"
-    task.finished_at = datetime.now()
+    task.finished_at = finished
     task.error_msg = error_msg
     if task.started_at:
-        task.duration = int((task.finished_at - task.started_at).total_seconds())
+        task.duration = int((finished - task.started_at).total_seconds())
     db.commit()
     db.refresh(task)
     return task
@@ -189,8 +191,9 @@ def run_creator_task(
     current_user=Depends(get_current_user)
 ):
     import threading
-    from datetime import datetime
+    from datetime import datetime, timezone
 
+    now = datetime.now(timezone.utc)
     task_id = f"task_{uuid.uuid4().hex[:16]}"
 
     task = ContentTask(
@@ -198,7 +201,7 @@ def run_creator_task(
         topic_id=topic_id,
         stage="creator",
         status="running",
-        started_at=datetime.now(),
+        started_at=now,
         created_by=current_user.username
     )
     db.add(task)
@@ -210,22 +213,22 @@ def run_creator_task(
     def _run():
         try:
             result = run_creator(topic_id)
-            from datetime import datetime
+            finished = datetime.now(timezone.utc)
             task.status = "completed"
-            task.finished_at = datetime.now()
+            task.finished_at = finished
             task.progress = 100
             task.message = "创作完成"
             task.result_data = result or {}
             if task.started_at:
-                task.duration = int((task.finished_at - task.started_at).total_seconds())
+                task.duration = int((finished - task.started_at).total_seconds())
             db.commit()
         except Exception as e:
-            from datetime import datetime
+            finished = datetime.now(timezone.utc)
             task.status = "failed"
-            task.finished_at = datetime.now()
+            task.finished_at = finished
             task.error_msg = str(e)
             if task.started_at:
-                task.duration = int((task.finished_at - task.started_at).total_seconds())
+                task.duration = int((finished - task.started_at).total_seconds())
             db.commit()
 
     thread = threading.Thread(target=_run)