Stop master-key peers from outliving their devices

A deleted master key could keep letting its devices in: ui.db learns what
is on a server only from awg-ctrl's reply, and a node that executed a
request whose 504/502 reply got lost, or a device deleted while a
reconcile pass was in flight, left a peer nothing remembered to remove.

- awg-ctrl: PUT /api/peers/sync takes a panel's full list of wanted keys
  and removes every other peer of that panel's area. Removal is driven
  only by such an explicit list, never by time or inactivity: a panel
  that is offline sends nothing, so nothing is deleted. Registered before
  PUT /api/peers/:pub, with its own 512 kB body limit.
- Every panel has a stable id (ui.db, mirrored to awg-ui/panel.id) and
  adds peers as "<panel>/m<key>/d<device>", so two panels on one awg-ctrl
  never touch each other's peers. Legacy "m1/d2" peers are claimed only
  when their key is in the panel's list.
- Each reconcile pass ends with the sync, built from ui.db at that moment.
  Its reply also self-heals: a device whose key is missing on a server
  (a rekey rolled back after a lost reply) is added again.
- Deleting a master key stops it at once but keeps it listed as
  "Удаляется — ждёт: …" until every server confirms, instead of saying
  "deleted" while an offline node still lets the devices in.
- Deleting a node reconciles it first; if it is offline or has not
  confirmed a deleted key, it takes ?force=1 and a warning. Tombstones
  are no longer dropped silently.
- /sub/v1: an unknown device gets a signed 410 revoked that does not count
  towards the failure limit (dead clients behind one node NAT used to
  lock everyone out), every response echoes the request's ts and device,
  and 401 reasons and the first 429 per window are logged. config and rev
  are unchanged, byte-identical on one server.
- CLI: `awg-ctrl peers [drop <area|legacy>]` lists and removes
  subscription peers by area; `join --no-panel` asks whether to keep or
  drop the panel's own peers (NODE_PEERS=keep|drop).

awg-ui/nodes.ts

@@ -148,6 +148,13 @@ export function createNodes(deps: { uidb: Database.Database; ctrlLocal: Ctrl; ba
     const onlineHandlers: ((id: number) => void)[] = [];
     const onOnline = (cb: (id: number) => void) => { onlineHandlers.push(cb); };
 
+    // Подписчики на «сервер удаляют»: подписка сперва снимает с него своих пиров и может
+    // запретить удаление. forcible — запрет снимается подтверждением оператора (force):
+    // сервер просто не всё успел подтвердить, а не используется.
+    type DeleteVeto = { error: string; forcible: boolean } | null;
+    const deleteHandlers: ((id: number, force: boolean) => Promise<DeleteVeto>)[] = [];
+    const beforeDelete = (cb: (id: number, force: boolean) => Promise<DeleteVeto>) => { deleteHandlers.push(cb); };
+
     /** Сервер по умолчанию: локальный, а без него — первая нода. */
     function defaultId(): number {
         if (LOCAL) return 0;
@@ -339,16 +346,23 @@ export function createNodes(deps: { uidb: Database.Database; ctrlLocal: Ctrl; ba
         res.json({ id, name });
     });
 
-    router.delete("/:id", (req: Request, res: Response) => {
+    router.delete("/:id", async (req: Request, res: Response) => {
         const id = idOf(req);
         const n = validId(id) ? q.byId.get(id) as NodeRow | undefined : undefined;
         if (!n) { res.status(404).json({ error: "Не найден" }); return; }
-        // Ключи API и мастер-ключи ссылаются на server_id — не оставляем их висеть в воздухе.
-        const used = (["api_keys", "master_servers"] as const).some(t => {
-            try { return (uidb.prepare(`SELECT COUNT(*) AS n FROM ${t} WHERE server_id = ?`).get(id) as { n: number }).n > 0; }
-            catch { return false; }
-        });
-        if (used) { res.status(409).json({ error: "К серверу привязаны ключи API или мастер-ключи — сначала удалите их" }); return; }
+        // Ключи API ссылаются на server_id — не оставляем их висеть в воздухе. Мастер-ключи
+        // проверяет подписка в своём обработчике.
+        let used = false;
+        try { used = (uidb.prepare("SELECT COUNT(*) AS n FROM api_keys WHERE server_id = ?").get(id) as { n: number }).n > 0; }
+        catch { /* таблицы ещё нет */ }
+        if (used) { res.status(409).json({ error: "К серверу привязаны ключи API — сначала удалите их" }); return; }
+        const force = req.query.force === "1";
+        for (const cb of deleteHandlers) {
+            let veto: DeleteVeto;
+            try { veto = await cb(id, force); } catch { veto = { error: "Не удалось подготовить сервер к удалению", forcible: true }; }
+            if (veto) { res.status(409).json({ error: veto.error, can_force: veto.forcible && !force }); return; }
+        }
+        if (!q.byId.get(id)) { res.status(404).json({ error: "Не найден" }); return; }
         const c = conns.get(id);
         if (c) { dropConn(id, c); c.ws.close(4004, "removed"); }
         q.delete.run(id);
@@ -359,5 +373,5 @@ export function createNodes(deps: { uidb: Database.Database; ctrlLocal: Ctrl; ba
         res.json({ success: true, id });
     });
 
-    return { router, ctrlFor, exists, isOnline, ids, onOnline, defaultId, start };
+    return { router, ctrlFor, exists, isOnline, ids, onOnline, beforeDelete, defaultId, start };
 }