#5: F2 sub-project 2 - IMAP SEARCH, EXPUNGE, COPY, MOVE

Adds the second F2 sub-project on top of the merged IMAP core: full
SEARCH criteria matching (flags, dates, size, headers, body/text,
NOT/OR), EXPUNGE (soft-delete via expunged_at), COPY, and MOVE (RFC
6851, advertised via CapMove/CapUIDPlus). Verified end-to-end with a
real go-imap/v2 client against embedded Postgres.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

services/protocols/internal/infrastructure/postgres/expunge_repository.go

@@ -0,0 +1,92 @@
+package postgres
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+// ExpungeRepository implements port.ExpungeRepository against Postgres.
+type ExpungeRepository struct {
+	pool *pgxpool.Pool
+}
+
+func NewExpungeRepository(pool *pgxpool.Pool) *ExpungeRepository {
+	return &ExpungeRepository{pool: pool}
+}
+
+// Expunge marks each message identified by (folderID, uid) in uids as
+// expunged, decrements the folder's total_count (and unread_count for any
+// message that lacked \Seen), and decrements the owning mailbox's
+// used_bytes by the message's size_bytes. used_bytes is logical,
+// message-level accounting (mirroring how delivery and COPY add to it per
+// message even when the underlying blob is deduplicated), so it is
+// decremented here independently of message_blobs.ref_count, whose
+// reclamation is deferred to a future GC task. One transaction per call;
+// each uid is processed sequentially within it.
+func (r *ExpungeRepository) Expunge(ctx context.Context, folderID string, uids []uint32) error {
+	if len(uids) == 0 {
+		return nil
+	}
+	tx, err := r.pool.Begin(ctx)
+	if err != nil {
+		return fmt.Errorf("begin transaction: %w", err)
+	}
+	defer tx.Rollback(ctx)
+
+	for _, uid := range uids {
+		var wasSeen bool
+		var mailboxID string
+		var sizeBytes int64
+		err := tx.QueryRow(ctx, `
+			SELECT EXISTS (
+				SELECT 1 FROM message_flags mf
+				JOIN email_messages m ON m.id = mf.message_id AND m.received_at = mf.received_at
+				WHERE m.folder_id = $1 AND m.uid = $2 AND mf.flag = '\Seen'
+			), m.mailbox_id, m.size_bytes
+			FROM email_messages m
+			WHERE m.folder_id = $1 AND m.uid = $2
+		`, folderID, uid).Scan(&wasSeen, &mailboxID, &sizeBytes)
+		if err != nil {
+			return fmt.Errorf("check seen flag for uid %d: %w", uid, err)
+		}
+
+		tag, err := tx.Exec(ctx, `
+			UPDATE email_messages SET expunged_at = NOW()
+			WHERE folder_id = $1 AND uid = $2 AND expunged_at IS NULL
+		`, folderID, uid)
+		if err != nil {
+			return fmt.Errorf("expunge uid %d: %w", uid, err)
+		}
+		if tag.RowsAffected() == 0 {
+			// Nothing to expunge (already expunged or never existed) - the
+			// caller already verified \Deleted, so don't touch counters for
+			// a message that wasn't actually there.
+			continue
+		}
+
+		unreadDelta := 0
+		if !wasSeen {
+			unreadDelta = 1
+		}
+		if _, err := tx.Exec(ctx, `
+			UPDATE folders SET total_count = total_count - 1, unread_count = unread_count - $1
+			WHERE id = $2
+		`, unreadDelta, folderID); err != nil {
+			return fmt.Errorf("decrement folder counters for uid %d: %w", uid, err)
+		}
+
+		if _, err := tx.Exec(ctx, `
+			UPDATE mailboxes SET used_bytes = used_bytes - $1
+			WHERE id = $2
+		`, sizeBytes, mailboxID); err != nil {
+			return fmt.Errorf("decrement mailbox used_bytes for uid %d: %w", uid, err)
+		}
+	}
+
+	if err := tx.Commit(ctx); err != nil {
+		return fmt.Errorf("commit: %w", err)
+	}
+	return nil
+}