feat(GODT-2289): UIDValidity as Timestamp

Update UIDValidity to be timestamp with the number of seconds since
the 1st of February 2023. This avoids the problem where we lose the
last UIDValidity value due to the vault being missing/corrupted/deleted.

internal/app/bridge.go

@@ -23,6 +23,7 @@ import (
 	"runtime"
 
 	"github.com/Masterminds/semver/v3"
+	"github.com/ProtonMail/gluon/imap"
 	"github.com/ProtonMail/go-autostart"
 	"github.com/ProtonMail/gopenpgp/v2/crypto"
 	"github.com/ProtonMail/proton-bridge/v3/internal/bridge"
@@ -110,6 +111,7 @@ func withBridge( //nolint:funlen
 		// Crash and report stuff
 		crashHandler,
 		reporter,
+		imap.DefaultEpochUIDValidityGenerator(),
 
 		// The logging stuff.
 		c.String(flagLogIMAP) == "client" || c.String(flagLogIMAP) == "all",