feat: AI并行处理 + 修复邮件丢失

- _ai_processor 改用 ThreadPoolExecutor(5 workers) 并行调用AI
- _tg_worker 每轮排空所有待发TG消息(原来每轮只取1条)
- fetch_unseen_emails 单封FETCH失败不再丢弃整个批次，跳过继续

main.py

@@ -5,6 +5,7 @@ import signal
 import sys
 import threading
 import time
+from concurrent.futures import ThreadPoolExecutor
 from src.config import load_config
 from src.summarizer import poll_accounts, ai_process, tg_send_and_mark
 from src.tg_bot import poll_telegram
@@ -64,21 +65,33 @@ def _email_poller(cfg):
 
 
 def _ai_processor(cfg):
-    logger.info("AI 处理线程已启动")
-    while _running:
-        try:
-            acct_idx, mail = _email_queue.get(timeout=1)
-        except queue_module.Empty:
-            continue
-        try:
-            info = ai_process(cfg, acct_idx, mail)
-            if info:
-                _tg_queue.put(info)
-        except Exception as e:
-            logger.error(f"AI 处理邮件失败: {e}", exc_info=True)
-        finally:
-            with _pending_lock:
-                _pending_uids.discard(mail.uid)
+    logger.info("AI 处理线程已启动 (并行 workers=5)")
+    max_workers = 5
+    with ThreadPoolExecutor(max_workers=max_workers) as executor:
+        pending_futures = {}
+        while _running:
+            while len(pending_futures) < max_workers:
+                try:
+                    acct_idx, mail = _email_queue.get_nowait()
+                except queue_module.Empty:
+                    break
+                future = executor.submit(ai_process, cfg, acct_idx, mail)
+                pending_futures[future] = (acct_idx, mail)
+
+            completed = [f for f in pending_futures if f.done()]
+            for future in completed:
+                acct_idx, mail = pending_futures.pop(future)
+                try:
+                    info = future.result()
+                    if info:
+                        _tg_queue.put(info)
+                except Exception as e:
+                    logger.error(f"AI 处理邮件失败: {e}", exc_info=True)
+                finally:
+                    with _pending_lock:
+                        _pending_uids.discard(mail.uid)
+
+            time.sleep(0.1 if pending_futures else 0.5)
 
 
 def _tg_worker(cfg):
@@ -90,13 +103,14 @@ def _tg_worker(cfg):
         except Exception as e:
             logger.error(f"TG 轮询错误: {e}", exc_info=True)
 
-        try:
-            info = _tg_queue.get_nowait()
-            tg_send_and_mark(cfg, info)
-        except queue_module.Empty:
-            pass
-        except Exception as e:
-            logger.error(f"TG 发送失败: {e}", exc_info=True)
+        while _running:
+            try:
+                info = _tg_queue.get_nowait()
+                tg_send_and_mark(cfg, info)
+            except queue_module.Empty:
+                break
+            except Exception as e:
+                logger.error(f"TG 发送失败: {e}", exc_info=True)
 
         if _running:
             time.sleep(1)