feat: init AI email summarization bot

- Multi-account IMAP email polling with UID tracking
- DeepSeek API integration with JSON Mode structured output
- Telegram notification with formatted MarkdownV2 message
- YAML config with dataclass-based type validation
- Graceful shutdown on SIGINT/SIGTERM
- 60s default polling interval

src/config.py

@@ -0,0 +1,54 @@
+from dataclasses import dataclass, field
+from typing import List
+import yaml
+
+
+@dataclass
+class EmailAccount:
+    imap_server: str
+    imap_port: int
+    username: str
+    password: str
+
+
+@dataclass
+class AIConfig:
+    api_key: str
+    model: str
+    base_url: str
+
+
+@dataclass
+class TelegramConfig:
+    bot_token: str
+    chat_id: str
+
+
+@dataclass
+class PollingConfig:
+    interval_seconds: int
+
+
+@dataclass
+class Config:
+    email_accounts: List[EmailAccount]
+    ai: AIConfig
+    telegram: TelegramConfig
+    polling: PollingConfig
+
+
+def load_config(path: str) -> Config:
+    with open(path, "r", encoding="utf-8") as f:
+        raw = yaml.safe_load(f)
+
+    accounts = [EmailAccount(**a) for a in raw["email_accounts"]]
+    ai = AIConfig(**raw["ai"])
+    tg = TelegramConfig(**raw["telegram"])
+    polling = PollingConfig(**raw["polling"])
+
+    return Config(
+        email_accounts=accounts,
+        ai=ai,
+        telegram=tg,
+        polling=polling,
+    )