Merge main into ui-refactor; port MDM support to the Wails UI

Integrates main's MDM configuration-profile feature and adapts it to the
Wails UI (this branch had already replaced the Fyne UI).

Conflict resolution:
- go.mod/go.sum: take main's deps; howett.net/plist pinned to v1.0.2-... (tidy)
- client/proto/daemon.pb.go: regenerated from the merged daemon.proto
- client/internal/peer/status.go: union of ipToKey (main) + sessionExpiresAt (HEAD)
- client/server/server.go: main's intent/liveness model (connectionGoroutineRunning,
  clientRunning no longer cleared by the goroutine) + empty-PSK guard
- client/ui/client_ui.go, client/ui/profile.go: removed (dead Fyne UI)

MDM port (backend + tray):
- services/settings.go: expose MDMManagedFields plus a managedFields map keyed
  by Config field names so the settings form can gate a control without
  translating mdm.Key* names
- tray: gate Profiles / Exit Node menus on DisableProfiles / DisableNetworks via
  GetFeatures, refreshed on the config_changed system event (replaces the legacy
  2s poll); localized MDM policy-applied toast in all shipped locales
- client/proto/metadata.go: shared constants for the config_changed /
  policy_applied event markers

PreSharedKey: GetConfig now returns preSharedKeySet (bool) instead of the masked
value; the settings form provides its own placeholder and sends a new key only
when the user types one.

client/internal/peer/status_test.go

@@ -90,12 +90,11 @@ func TestStatus_PeerStateByIP_MatchesIPv6(t *testing.T) {
 	req.Equal("pk-1", state.PubKey, "matching state must carry the right pub key")
 }
 
-// TestStatus_PeerStateByIP_MatchesOfflinePeers covers peers that have
-// been moved into the offline slice via ReplaceOfflinePeers. Callers
-// (DNS filter, embed.Client.IdentityForIP) need to treat them as known
-// rather than unknown — otherwise authentication / DNS filtering treats
-// known-but-offline peers as foreign IPs.
-func TestStatus_PeerStateByIP_MatchesOfflinePeers(t *testing.T) {
+// TestStatus_PeerStateByIP_IgnoresOfflinePeers documents that peers
+// moved into the offline slice via ReplaceOfflinePeers are intentionally
+// not resolvable by IP: only active peers can carry traffic, so callers
+// (DNS filter, embed.Client.IdentityForIP) treat them as unknown.
+func TestStatus_PeerStateByIP_IgnoresOfflinePeers(t *testing.T) {
 	status := NewRecorder("https://mgm")
 	req := require.New(t)
 
@@ -103,13 +102,31 @@ func TestStatus_PeerStateByIP_MatchesOfflinePeers(t *testing.T) {
 		{PubKey: "pk-offline", FQDN: "offline.netbird", IP: "100.64.0.20", IPv6: "fd00::20"},
 	})
 
-	state, ok := status.PeerStateByIP("100.64.0.20")
-	req.True(ok, "offline peer must resolve by IPv4 tunnel address")
-	req.Equal("pk-offline", state.PubKey, "matching state must carry the offline peer's pub key")
+	_, ok := status.PeerStateByIP("100.64.0.20")
+	req.False(ok, "offline peer must not resolve by IPv4 tunnel address")
 
-	state, ok = status.PeerStateByIP("fd00::20")
-	req.True(ok, "offline peer must resolve by IPv6 tunnel address")
-	req.Equal("pk-offline", state.PubKey, "IPv6 match must carry the offline peer's pub key")
+	_, ok = status.PeerStateByIP("fd00::20")
+	req.False(ok, "offline peer must not resolve by IPv6 tunnel address")
+}
+
+// TestStatus_PeerStateByIP_RemovedPeer verifies RemovePeer drops the
+// IP index entries for both address families.
+func TestStatus_PeerStateByIP_RemovedPeer(t *testing.T) {
+	status := NewRecorder("https://mgm")
+	req := require.New(t)
+
+	req.NoError(status.AddPeer("pk-1", "peer-1.netbird", "100.64.0.10", "fd00::1"))
+
+	_, ok := status.PeerStateByIP("100.64.0.10")
+	req.True(ok, "active peer must resolve before removal")
+
+	req.NoError(status.RemovePeer("pk-1"))
+
+	_, ok = status.PeerStateByIP("100.64.0.10")
+	req.False(ok, "removed peer must not resolve by IPv4 tunnel address")
+
+	_, ok = status.PeerStateByIP("fd00::1")
+	req.False(ok, "removed peer must not resolve by IPv6 tunnel address")
 }
 
 func TestStatus_UpdatePeerFQDN(t *testing.T) {