Create, rename and remove the devices that dial in

On a tunnel this machine configures — today that means OpenWrt's UCI, which is
where the server here lives — the VPN tab can add a device, rename it and take
it away. A wg-quick host is reported as unmanaged and shows no buttons, because
half-supporting a second configuration format is worse than an honest refusal.

Adding generates the keypair and a pre-shared key on the machine, picks the
lowest free address in the tunnel's range, and hands back the complete client
profile with a QR code for the WireGuard apps. The private key in it is
generated for that one call and stored nowhere, so the profile is shown until
dismissed and then gone — the same bargain as any password this console makes.

Nothing restarts the network, which matters when the interface belongs to the
router the house is behind. `uci commit` writes the file and applies nothing;
`wg set` changes one peer on the live interface and touches nothing else.

The order of the two is chosen so they cannot disagree quietly. Adding writes
the configuration first and rolls it back if the live tunnel refuses, because a
device that works only after the next reboot is the worst of the three outcomes.
Removing does the live tunnel first, since that is the moment access actually
ends, and says plainly if the configuration half then fails.

Removing asks for the device's name to be typed back, at both ends. It is the
one action here that cannot be undone and it sits one tap from a list of devices
that all look alike.

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

internal/vpn/vpn.go

@@ -46,11 +46,17 @@ type Peer struct {
 	Keepalive int   `json:"keepalive,omitempty"`
 	// PSK notes that a pre-shared key is in use, without the key itself going anywhere.
 	PSK bool `json:"psk,omitempty"`
+	// Section is the configuration section holding this peer, and the identifier anything that
+	// edits it uses. Empty when the peer is not in a configuration this can edit.
+	Section string `json:"section,omitempty"`
 }
 
 // Tunnel is one WireGuard interface.
 type Tunnel struct {
-	Name      string `json:"name"`
+	Name string `json:"name"`
+	// Managed is whether devices on this tunnel can be added and removed from here, which
+	// today means its peers are configured through OpenWrt's UCI.
+	Managed   bool   `json:"managed"`
 	PublicKey string `json:"public_key"`
 	// Kind is "server" when peers dial in to this machine, "client" when this machine dials
 	// out through a peer, and "" when it is too new or too odd to tell. It is worked out from
@@ -113,6 +119,7 @@ func Look(ctx context.Context) Report {
 			p.Online = p.Handshake != nil && time.Since(*p.Handshake) < onlineWithin
 		}
 		t.Kind, t.Exit = classify(*t)
+		t.Managed = Managed(ctx, t)
 		sort.SliceStable(t.Peers, func(a, b int) bool {
 			pa, pb := t.Peers[a], t.Peers[b]
 			if pa.Online != pb.Online {