fix: 内存误判(psutil→GlobalMemoryStatusEx) + 时间戳硬截止(>30min丢弃)

- easyocr_worker.py: 删除psutil物理内存检查，统一使用GlobalMemoryStatusEx
  (Windows上psutil可比Task Manager少报~1.7GB，导致4.2GB可用误判为2.5GB)
- monitor.py: _ocr_text_has_fresh_timestamp()加硬截止——最新时间戳>1800s(30min)
  无论是否含CJK均丢弃，修复15:09看到13:34消息(90min前)被误回复
- 新增_timestamp_age_seconds()辅助方法

easyocr_worker.py

@@ -99,39 +99,38 @@ try:
 
     # ── 预检：物理内存+虚拟内存是否足够加载 CUDA 库 ──
     _vm = _get_virtual_memory_info()
-    # 检查物理内存：CUDA加载需要足够物理内存，否则会使用页面文件导致冻结
-    try:
-        import psutil
-        _mem = psutil.virtual_memory()
-        _avail_phys_gb = _mem.available / (1024**3)
-        _used_phys_gb = _mem.used / (1024**3)
-        _total_phys_gb = _mem.total / (1024**3)
-        # ⭐ 页面文件百分比 + 总提交量检查：防页面文件94%+时仍尝试CUDA导致冻结
-        _pagefile_pct = _vm.get("commit_pct", 0) if _vm else 0
-        _pagefile_used_gb = _total_phys_gb + (_vm.get("total_pagefile_gb", 0) - _vm.get("avail_pagefile_gb", 0)) - _avail_phys_gb if _vm else 0
-        _commit_gb = _used_phys_gb + (_vm.get("total_pagefile_gb", 0) - _vm.get("avail_pagefile_gb", 0)) if _vm else _used_phys_gb
-        if _pagefile_pct > 85.0 or _commit_gb > _total_phys_gb * 1.5:
-            _msg = (
-                f"系统内存压力过高: 物理剩余{_avail_phys_gb:.1f}GB({_mem.percent}%)，"
-                f"页面文件已用{_pagefile_pct}%，总提交{_commit_gb:.1f}GB>{_total_phys_gb*1.5:.1f}GB阈值"
-            )
-            _write_crash_log(f"{datetime.now()} [easyocr_worker] 系统内存压力预检失败: {_msg}")
-            os.environ["EASYOCR_FORCE_CPU"] = "1"
-            sys.stderr.write(f"[easyocr_worker] ⚠️ {_msg}，降级CPU模式\n")
-            sys.stderr.flush()
-        elif _avail_phys_gb < 3.0:
-            _msg = (
-                f"物理内存不足: 剩余{_avail_phys_gb:.1f}GB"
-                f"(总计{_total_phys_gb:.1f}GB，使用{_mem.percent}%)"
-                f"，CUDA加载需要≥3GB物理内存"
-            )
-            _write_crash_log(f"{datetime.now()} [easyocr_worker] 物理内存预检失败: {_msg}")
-            # 设置环境变量强制CPU模式，而不是直接退出
-            os.environ["EASYOCR_FORCE_CPU"] = "1"
-            sys.stderr.write(f"[easyocr_worker] ⚠️ {_msg}，降级CPU模式\n")
-            sys.stderr.flush()
-    except Exception:
-        pass  # psutil不可用时不阻断
+    # ⭐ 统一使用 GlobalMemoryStatusEx（与 monitor.py / Task Manager 一致）
+    #    psutil.virtual_memory().available 在 Windows 上可比 Task Manager 少报 ~1.7GB，
+    #    导致 4.2GB 可用时误判为 2.5GB 触发降级。
+    if _vm:
+        try:
+            _avail_phys_gb = _vm.get("avail_phys_gb", 0)
+            _total_phys_gb = _vm.get("total_phys_gb", 0)
+            _used_phys_gb = _total_phys_gb - _avail_phys_gb
+            _pagefile_pct = _vm.get("commit_pct", 0)
+            _pagefile_used_gb = _vm.get("total_pagefile_gb", 0) - _vm.get("avail_pagefile_gb", 0)
+            _commit_gb = _used_phys_gb + _pagefile_used_gb
+            if _pagefile_pct > 85.0 or _commit_gb > _total_phys_gb * 1.5:
+                _msg = (
+                    f"系统内存压力过高: 物理剩余{_avail_phys_gb:.1f}GB，"
+                    f"页面文件已用{_pagefile_pct}%，总提交{_commit_gb:.1f}GB>{_total_phys_gb*1.5:.1f}GB阈值"
+                )
+                _write_crash_log(f"{datetime.now()} [easyocr_worker] 系统内存压力预检失败: {_msg}")
+                os.environ["EASYOCR_FORCE_CPU"] = "1"
+                sys.stderr.write(f"[easyocr_worker] ⚠️ {_msg}，降级CPU模式\n")
+                sys.stderr.flush()
+            elif _avail_phys_gb < 3.0:
+                _msg = (
+                    f"物理内存不足: 剩余{_avail_phys_gb:.1f}GB"
+                    f"(总计{_total_phys_gb:.1f}GB)"
+                    f"，CUDA加载需要≥3GB物理内存"
+                )
+                _write_crash_log(f"{datetime.now()} [easyocr_worker] 物理内存预检失败: {_msg}")
+                os.environ["EASYOCR_FORCE_CPU"] = "1"
+                sys.stderr.write(f"[easyocr_worker] ⚠️ {_msg}，降级CPU模式\n")
+                sys.stderr.flush()
+        except Exception:
+            pass  # GlobalMemoryStatusEx 失败时不阻断
     # ⭐ 检查页面文件：百分比>85% 或 剩余<2GB 时退出（防冻结）
     if _vm and (_vm.get("commit_pct", 0) > 85.0 or _vm.get("avail_pagefile_gb", 99) < 2.0):
         _msg = (