feat: IMAP mail sync with thread-to-contact matching (PRD §6.1)

Real IMAP connection via imapflow library:
- Connects to IMAP server (IMAPFlow, TLS on port 993)
- Fetches recent messages (configurable limit, default 20)
- Extracts: from, fromEmail, subject, date, snippet (200 chars)
- Thread-to-contact matching (PRD §6.1):
  1. Match sender email against persons table
  2. If no person match, extract domain and match against company.website
  3. Returns matchedCompany + matchedPerson for each email
- Audit-logged (action: crm.mailsync:imap)
- Zod validated (host, port, user, password, folder, limit)
- 502 on IMAP connection failure with detail
- 400 on validation failure

Tested: invalid creds → 502 'IMAP connection failed', missing host → 400

skills/aminer-daily-paper/scripts/constants.py

@@ -0,0 +1,7 @@
+from __future__ import annotations
+
+DEFAULT_TOP_K = 10
+
+AMINER_AUTHOR_URL_TEMPLATE = "https://www.aminer.cn/profile/{author_id}"
+AMINER_PAPER_URL_TEMPLATE = "https://www.aminer.cn/pub/{paper_id}"
+DEFAULT_REC5_URL = "https://publicapi.chatglm.cn/chatglm_public/skill/aminer/api/v3/paper/rec5"