fix(imap): fix mojibake in nested emails, empty headers, and date handling (#909)

* fix(imap): fix mojibake in nested emails, empty headers, and date handling

- Add line-by-line mojibake fix fallback for complex emails with mixed content
- Apply empty header cleanup globally to fix nested message/rfc822 parts
- Add locale-independent date formatting (format_imap_date, format_rfc2822_date)
- Fill missing Date header from created_at field
- Fix getSubPart for non-multipart messages
- Accept CREATE requests from clients (e.g. Gmail creating Drafts)
- Strip whitespace from IMAP password
- Use MIMEText instead of MIMEMultipart for sent mail generation
- Keep body in original CTE encoding for correct BODYSTRUCTURE
- Update CHANGELOG (zh/en)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* docs: consolidate IMAP changelog entries into single line

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

smtp_proxy_server/imap_mailbox.py

@@ -10,7 +10,7 @@ from zope.interface import implementer
 from config import settings
 from imap_http_client import BackendClient
 from imap_message import SimpleMessage
-from parse_email import generate_email_model, parse_email
+from parse_email import generate_email_model, parse_email, clean_raw_headers, fix_mojibake
 
 _logger = logging.getLogger(__name__)
 _logger.setLevel(logging.INFO)
@@ -246,6 +246,8 @@ class SimpleMailbox:
                 try:
                     if self.name == "INBOX":
                         raw = item.get("raw", "")
+                        raw = fix_mojibake(raw)
+                        raw = clean_raw_headers(raw)
                         email_model = parse_email(raw)
                     elif self.name == "SENT":
                         email_model, raw = generate_email_model(item)
@@ -256,7 +258,8 @@ class SimpleMailbox:
                         self._flags[uid_val] = {r"\Seen"}
                     flags = self._flags[uid_val]
                     msg = SimpleMessage(
-                        uid_val, email_model, flags=flags, raw=raw
+                        uid_val, email_model, flags=flags, raw=raw,
+                        created_at=item.get("created_at"),
                     )
                     self._cache.put(uid_val, msg)
                 except Exception as e: