feat: interactive inline buttons, SMTP reply, AI reply suggestions

- Inline keyboard: view original / back to summary toggle per message
- SMTP config per account for sending replies
- Reply button: click, type message, auto-send via SMTP
- AI Reply button: generates 3 suggestions via DeepSeek
  - Simple replies (OK, Got it) send immediately on tap
  - Substantive replies require confirm before send
  - Hides AI Reply button when AI determines reply unnecessary
- Telegram long polling integrated into main loop for real-time interaction

src/ai_client.py

@@ -40,6 +40,49 @@ def summarize_email(ai_cfg: AIConfig, recipient: str, subject: str, sender: str,
         "Content-Type": "application/json",
     }
 
+    return _call_deepseek(ai_cfg, payload)
+
+
+REPLY_PROMPT = """你是一个邮件回复助手。根据以下邮件内容生成3个建议回复。
+
+返回 JSON:
+{
+  "can_reply": true/false,
+  "suggestions": [
+    {"text": "回复内容", "is_simple": true/false},
+    {"text": "回复内容", "is_simple": true/false},
+    {"text": "回复内容", "is_simple": true/false}
+  ]
+}
+
+- can_reply 为 false 时表示无需回复或不适合自动建议（此时忽略 suggestions）
+- is_simple 为 true 表示纯确认性回复（如"好的""收到""明白"），用户选择后可直接发送
+- is_simple 为 false 表示涉及实质内容，需要用户确认后再发送
+- 每条回复控制在 50 字以内
+只返回 JSON，不要包含任何其他文字。"""
+
+
+@retry()
+def generate_reply_suggestions(ai_cfg: AIConfig, sender: str, subject: str, body: str) -> dict:
+    content = f"发件人: {sender}\n主题: {subject}\n正文:\n{body[:4000]}"
+
+    payload = {
+        "model": ai_cfg.model,
+        "messages": [
+            {"role": "system", "content": REPLY_PROMPT},
+            {"role": "user", "content": content},
+        ],
+        "response_format": {"type": "json_object"},
+    }
+
+    return _call_deepseek(ai_cfg, payload)
+
+
+def _call_deepseek(ai_cfg: AIConfig, payload: dict) -> dict:
+    headers = {
+        "Authorization": f"Bearer {ai_cfg.api_key}",
+        "Content-Type": "application/json",
+    }
     resp = requests.post(
         f"{ai_cfg.base_url.rstrip('/')}/chat/completions",
         headers=headers,