Add VPS IMAP sorting automation

Prompts used since the previous commit:
- Hieronder staat je oorspronkelijke plan. Volgens mij moet stap 'Add VPS automation' nog worden uitgevoerd, inclusief de testen.

Special observations:
- Added a testable IMAP sorting daemon, shared IMAP operation helpers, systemd service template, and SSH deployment script.
- Local tests passed; no live VPS deployment or mailbox-affecting daemon test was run.
- verplaats_log.json remains modified from the user's run and was intentionally not staged.

mail_imap_ops.py

@@ -0,0 +1,88 @@
+"""Shared IMAP operations used by mailcat sorters."""
+
+from __future__ import annotations
+
+import email
+import email.header
+from email.message import Message
+
+from imap_utils import quote_mailbox
+from mail_routes import PREFIX, quarter_folder, route_from_subject
+
+
+HEADER_FETCH = "(BODY.PEEK[HEADER.FIELDS (FROM SUBJECT DATE)])"
+
+
+def decode_header_value(value) -> str:
+    """Decode an RFC 2047 header value into display text."""
+    if not value:
+        return ""
+    try:
+        parts = email.header.decode_header(value)
+        out = []
+        for raw, charset in parts:
+            if isinstance(raw, bytes):
+                out.append(raw.decode(charset or "utf-8", errors="replace"))
+            else:
+                out.append(str(raw))
+        return " ".join(out).strip()
+    except Exception:
+        return str(value or "")
+
+
+def fetch_body(data) -> bytes | None:
+    """Return the first bytes payload from an IMAP FETCH response."""
+    if not data:
+        return None
+    for item in data:
+        if isinstance(item, tuple) and len(item) >= 2 and isinstance(item[1], bytes):
+            return item[1]
+    return None
+
+
+def parse_header(raw_header: bytes) -> Message:
+    """Parse an IMAP header payload into an email Message."""
+    return email.message_from_bytes(raw_header)
+
+
+def destination_from_header(raw_header: bytes) -> str | None:
+    """Return the full IMAP destination folder for a fetched header."""
+    msg = parse_header(raw_header)
+    from_raw = decode_header_value(msg.get("From", ""))
+    subject = decode_header_value(msg.get("Subject", ""))
+    date_str = msg.get("Date", "")
+
+    destination = route_from_subject(from_raw, subject)
+    if destination == "__FACTUUR_DATE__":
+        destination = quarter_folder(date_str)
+    if destination:
+        return PREFIX + destination
+    return None
+
+
+def ensure_mailbox(mail, folder: str) -> bool:
+    """Create a mailbox and its parents if they do not already exist."""
+    parts = folder.split(".")
+    for index in range(1, len(parts) + 1):
+        parent = ".".join(parts[:index])
+        status, _ = mail.create(quote_mailbox(parent))
+        if status not in {"OK", "NO"}:
+            return False
+    return True
+
+
+def move_message(mail, uid: bytes, src: str, dst: str):
+    """Copy a message to dst and mark it deleted in src."""
+    select_status, select_data = mail.select(quote_mailbox(src))
+    if select_status != "OK":
+        return False, ("select_source", select_status, select_data)
+
+    copy_status, copy_data = mail.uid("COPY", uid, quote_mailbox(dst))
+    if copy_status != "OK":
+        return False, ("copy", copy_status, copy_data)
+
+    store_status, store_data = mail.uid("STORE", uid, "+FLAGS", "\\Deleted")
+    if store_status != "OK":
+        return False, ("store_deleted", store_status, store_data)
+
+    return True, None