Phase 6: rules editor + unsubscribe detection (AUD-72)

- FR-11 rules editor: plain-text area at /rules, saved and versioned
  (SaveRules appends a version; restore re-saves an old version), parse
  errors surfaced, one-click re-classify. The reply model now reads the
  rules document too (FR-11).
- FR-7 unsubscribe: parse and store List-Unsubscribe / List-Unsubscribe-Post
  (migration v6), detect email and web links (internal/unsubscribe), a
  domain-level ignore list, and an explicit record of what was marked. No
  code path contacts an unsubscribe link; acting on one needs Sam's approval.
- Migration v6 is additive; unsubscribe gains url/updated_at.
- Tests: detector, parser, store migration/records/candidates, rules editor,
  unsubscribe handlers, message-detail rendering.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

internal/store/messages.go

@@ -20,15 +20,19 @@ type Message struct {
 	// MessageIDHeader is the RFC822 Message-ID header (Phase 5, FR-8). A reply
 	// uses it for In-Reply-To and References so Gmail keeps the thread.
 	MessageIDHeader string
-	FromAddr        string
-	ToAddr          string
-	Subject         string
-	BodyText        string
-	SourceAddress   string
-	DateSent        time.Time
-	ReceivedAt      time.Time
-	IMAPUID         int64
-	IMAPUIDValidity int64
+	// ListUnsubscribe and ListUnsubscribePost are the raw RFC 2369/8058 headers
+	// (Phase 6, FR-7). Detection runs over them on demand.
+	ListUnsubscribe     string
+	ListUnsubscribePost string
+	FromAddr            string
+	ToAddr              string
+	Subject             string
+	BodyText            string
+	SourceAddress       string
+	DateSent            time.Time
+	ReceivedAt          time.Time
+	IMAPUID             int64
+	IMAPUIDValidity     int64
 	// Folder is the app folder the message is filed under (Phase 4, FR-6/FR-9):
 	// inbox, delete, saved, or replied.
 	Folder string
@@ -71,19 +75,22 @@ func (s *Store) UpsertMessage(ctx context.Context, m *Message) (int64, error) {
 	const q = `
 INSERT INTO messages (
     gmail_id, thread_id, message_id_header, from_addr, to_addr, subject, body_text,
-    source_address, date_sent, received_at, imap_uid, imap_uidvalidity
-) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
+    source_address, list_unsubscribe, list_unsubscribe_post, date_sent, received_at,
+    imap_uid, imap_uidvalidity
+) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)
 ON CONFLICT (gmail_id) DO UPDATE SET
-    thread_id         = excluded.thread_id,
-    message_id_header = excluded.message_id_header,
-    from_addr         = excluded.from_addr,
-    to_addr           = excluded.to_addr,
-    subject           = excluded.subject,
-    body_text         = excluded.body_text,
-    source_address    = excluded.source_address,
-    date_sent         = excluded.date_sent,
-    imap_uid          = excluded.imap_uid,
-    imap_uidvalidity  = excluded.imap_uidvalidity`
+    thread_id             = excluded.thread_id,
+    message_id_header     = excluded.message_id_header,
+    from_addr             = excluded.from_addr,
+    to_addr               = excluded.to_addr,
+    subject               = excluded.subject,
+    body_text             = excluded.body_text,
+    source_address        = excluded.source_address,
+    list_unsubscribe      = excluded.list_unsubscribe,
+    list_unsubscribe_post = excluded.list_unsubscribe_post,
+    date_sent             = excluded.date_sent,
+    imap_uid              = excluded.imap_uid,
+    imap_uidvalidity      = excluded.imap_uidvalidity`
 
 	receivedAt := m.ReceivedAt
 	if receivedAt.IsZero() {
@@ -98,6 +105,8 @@ ON CONFLICT (gmail_id) DO UPDATE SET
 		nullString(m.Subject),
 		nullString(m.BodyText),
 		nullString(m.SourceAddress),
+		nullString(m.ListUnsubscribe),
+		nullString(m.ListUnsubscribePost),
 		nullTime(m.DateSent),
 		receivedAt.UTC().Format(sqlTimeLayout),
 		m.IMAPUID,
@@ -124,7 +133,8 @@ SELECT m.id, m.gmail_id, COALESCE(m.thread_id, ''), COALESCE(m.from_addr, ''),
        COALESCE(m.source_address, ''), COALESCE(m.date_sent, ''), m.received_at,
        COALESCE(m.imap_uid, 0), COALESCE(m.imap_uidvalidity, 0),
        COALESCE(m.folder, 'inbox'), COALESCE(m.mailbox, 'INBOX'),
-       COALESCE(m.message_id_header, '')
+       COALESCE(m.message_id_header, ''),
+       COALESCE(m.list_unsubscribe, ''), COALESCE(m.list_unsubscribe_post, '')
 FROM messages m WHERE m.id = ?`
 	var (
 		m        Message
@@ -135,6 +145,7 @@ FROM messages m WHERE m.id = ?`
 		&m.ID, &m.GmailID, &m.ThreadID, &m.FromAddr, &m.ToAddr, &m.Subject,
 		&m.BodyText, &m.SourceAddress, &dateSent, &received,
 		&m.IMAPUID, &m.IMAPUIDValidity, &m.Folder, &m.Mailbox, &m.MessageIDHeader,
+		&m.ListUnsubscribe, &m.ListUnsubscribePost,
 	)
 	if err != nil {
 		return Message{}, fmt.Errorf("load message %d: %w", id, err)