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/coding-agent/planning.md

@@ -0,0 +1,31 @@
+# Planning Reference
+
+Consult when breaking down a multi-step request.
+
+## When to Plan
+- Multiple files or components
+- Dependencies between parts
+- UI that needs visual verification
+- User says "build", "create", "implement"
+
+## Step Format
+```
+Step N: [What]
+- Output: [What exists after]
+- Test: [How to verify]
+```
+
+## Good Steps
+- Clear output (file, endpoint, screen)
+- Testable independently
+- No ambiguity in what "done" means
+
+## Bad Steps
+- "Implement the thing" (vague output)
+- No test defined
+- Depends on undefined prior step
+
+## Don't Plan
+- One-liner functions
+- Simple modifications
+- Questions about existing code