[client] UI refactor (#6069)

Refactor UI

---------

Co-authored-by: Eduard Gert <kontakt@eduardgert.de>
Co-authored-by: braginini <bangvalo@gmail.com>
Co-authored-by: Pascal Fischer <32096965+pascal-fischer@users.noreply.github.com>
Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: riccardom <riccardomanfrin@gmail.com>

client/ui/authsession/warning.go

@@ -0,0 +1,64 @@
+//go:build !android && !ios && !freebsd && !js
+
+// Package authsession holds the UI-side domain logic for the SSO
+// session-extend feature. The Wails facades in client/ui/services/session*.go
+// are thin adapters over these types.
+package authsession
+
+import (
+	"time"
+
+	"github.com/netbirdio/netbird/client/internal/auth/sessionwatch"
+)
+
+// Re-exported from sessionwatch so UI-side consumers don't import the
+// daemon-internal package directly.
+const (
+	MetaWarning          = sessionwatch.MetaSessionWarning
+	MetaFinal            = sessionwatch.MetaSessionFinal
+	MetaExpiresAt        = sessionwatch.MetaSessionExpiresAt
+	MetaLeadMinutes      = sessionwatch.MetaSessionLeadMinutes
+	MetaDeadlineRejected = sessionwatch.MetaSessionDeadlineRejected
+)
+
+// Warning is the typed payload emitted on the session-warning Wails events.
+type Warning struct {
+	// Absolute UTC deadline; best-effort, stays zero when metadata is
+	// missing or malformed (e.g. an older daemon) and the UI falls back
+	// to the Status snapshot.
+	ExpiresAt time.Time `json:"sessionExpiresAt"`
+	// Configured lead time, so the UI need not hardcode the constant.
+	LeadMinutes int `json:"leadMinutes"`
+	// True on the final-warning fallback event.
+	Final bool `json:"final"`
+}
+
+// WarningFromMetadata parses SystemEvent metadata into a Warning, or returns
+// (nil, false) when the event is not a session-warning. A field that fails to
+// parse stays zero; the event is still surfaced.
+func WarningFromMetadata(meta map[string]string) (*Warning, bool) {
+	if meta == nil || meta[MetaWarning] != "true" {
+		return nil, false
+	}
+
+	out := &Warning{
+		Final: meta[MetaFinal] == "true",
+	}
+	if raw := meta[MetaExpiresAt]; raw != "" {
+		if t, err := sessionwatch.ParseExpiresAt(raw); err == nil {
+			out.ExpiresAt = t
+		}
+	}
+	if raw := meta[MetaLeadMinutes]; raw != "" {
+		if n, err := sessionwatch.ParseLeadMinutes(raw); err == nil {
+			out.LeadMinutes = n
+		}
+	}
+	return out, true
+}
+
+// ParseExpiresAt re-exports sessionwatch.ParseExpiresAt so UI-side call sites
+// don't import the daemon-internal package.
+func ParseExpiresAt(s string) (time.Time, error) {
+	return sessionwatch.ParseExpiresAt(s)
+}