added IMAP, LetsEncrypt, update layout

internal/imapserver/backend.go

@@ -0,0 +1,25 @@
+// Package imapserver implements a minimal read-mostly IMAP4rev1 server backed by
+// internal/mailstore, so a mail client (Thunderbird etc.) can retrieve mail this
+// server received into a local mailbox. Only a single fixed "INBOX" folder is
+// supported — no folder hierarchy yet (aliases/multiple folders are a later
+// milestone). Login only accepts an app password (esrv_mailbox_app_passwords), never
+// a mailbox's own portal password, since IMAP AUTH has no interactive MFA step.
+package imapserver
+
+import (
+	"mailgoserver/internal/db"
+	"mailgoserver/internal/mailstore"
+	"mailgoserver/internal/toolbox"
+)
+
+// Backend holds the shared dependencies every connection's Session uses, mirroring
+// smtpserver.Backend.
+type Backend struct {
+	DB        *db.DB
+	Mailstore *mailstore.Store
+	Logger    *toolbox.Logger
+}
+
+func (b *Backend) NewSession() *Session {
+	return &Session{backend: b}
+}