Add real relay-level takedown (NIP-86 banevent) for admin deletes

The community relay goskatespots.nostr1.com runs on relay.tools, which
implements the NIP-86 Relay Management API. As the relay owner/moderator,
an admin can genuinely remove an event from the relay's database via
`banevent` — unlike a NIP-09 kind:5 request that most relays ignore for
non-authors.

- New src/lib/relayAdmin.ts: NIP-86 JSON-RPC client with NIP-98 HTTP auth
  (kind:27235 signed by the user's signer, payload hash included per
  NIP-86). Includes banEventOnRelay + getRelaySupportedMethods, with a
  CORS-proxy fallback for WebView contexts.
- useDeleteEntity admin path now also fires banEventOnRelay in the
  background (best-effort, never blocks the spinner), so admin takedowns
  actually erase the event from our own relay in addition to the kind:5
  request, optimistic local hide, and cross-device kind:1985 label.

Co-authored-by: shakespeare.diy <assistant@shakespeare.diy>

src/hooks/useDeleteEntity.ts

@@ -7,6 +7,7 @@ import {
   MODERATION_LABEL_HIDDEN,
 } from '@/lib/types';
 import { addLocalHidden } from '@/lib/localModeration';
+import { banEventOnRelay } from '@/lib/relayAdmin';
 import type { NostrEvent } from '@nostrify/nostrify';
 
 /**
@@ -143,6 +144,25 @@ export function useDeleteEntity() {
             labelError,
           );
         });
+
+        // REAL takedown on our own relay (NIP-86 `banevent`). Because the admin
+        // is the relay owner/moderator, goskatespots.nostr1.com honors this and
+        // actually removes the event from its database — unlike a cross-author
+        // kind:5 request. Also background/best-effort so it never blocks the UI;
+        // this may prompt one more signer approval (NIP-98 auth event).
+        if (user.signer) {
+          void banEventOnRelay({
+            signer: user.signer,
+            eventId: event.id,
+            reason: reason?.trim() || 'Removed by SkateSpots admin',
+          }).catch((banError) => {
+            console.warn(
+              '[useDeleteEntity] relay banevent failed (content is hidden in-app ' +
+                'regardless; you can retry from the relay moderator portal):',
+              banError,
+            );
+          });
+        }
       }
   }
 }

src/lib/relayAdmin.ts

@@ -0,0 +1,153 @@
+/**
+ * NIP-86 Relay Management API client (with NIP-98 HTTP auth).
+ *
+ * The SkateSpots community relay (goskatespots.nostr1.com) runs on relay.tools,
+ * which implements the NIP-86 management API. As the relay OWNER (or an assigned
+ * moderator), an admin can genuinely remove an event from the relay's database —
+ * not merely publish a best-effort kind:5 deletion request that other relays may
+ * ignore. `banevent` is the method that does this.
+ *
+ * Auth is a NIP-98 kind:27235 event signed by the caller (via their Amber /
+ * NIP-07 / nsec signer). The relay checks the signer's pubkey against its owner
+ * / moderator list, so only genuine admins can act.
+ *
+ * Docs: NIP-86 (relay management), NIP-98 (HTTP auth).
+ */
+
+import { sha256 } from '@noble/hashes/sha2.js';
+import { bytesToHex } from '@noble/hashes/utils.js';
+import { SKATE_RELAY } from '@/lib/types';
+import type { NostrSigner } from '@nostrify/nostrify';
+
+/** wss:// → https:// (the management API lives on the same URI as the socket). */
+function relayHttpUrl(wss: string): string {
+  return wss.replace(/^wss:\/\//i, 'https://').replace(/^ws:\/\//i, 'http://');
+}
+
+/** Base64-encode a UTF-8 string (browser-safe). */
+function base64(json: string): string {
+  // btoa needs a binary string; encode UTF-8 first.
+  const bytes = new TextEncoder().encode(json);
+  let bin = '';
+  for (const b of bytes) bin += String.fromCharCode(b);
+  return btoa(bin);
+}
+
+interface Nip86Response<T> {
+  result?: T;
+  error?: string;
+}
+
+/**
+ * Perform a single NIP-86 JSON-RPC call against a relay's HTTP endpoint,
+ * authenticated with a freshly-signed NIP-98 event.
+ *
+ * @throws if the network request fails, auth is rejected (401), or the relay
+ *         returns an `error` field.
+ */
+export async function relayManagementCall<T = unknown>(opts: {
+  signer: NostrSigner;
+  method: string;
+  params: unknown[];
+  relayWss?: string;
+  signal?: AbortSignal;
+}): Promise<T> {
+  const { signer, method, params, relayWss = SKATE_RELAY, signal } = opts;
+
+  const url = relayHttpUrl(relayWss);
+  const body = JSON.stringify({ method, params });
+
+  // NIP-98: kind 27235, tags u + method (+ payload hash, required by NIP-86).
+  const payloadHash = bytesToHex(sha256(new TextEncoder().encode(body)));
+  const authEvent = await signer.signEvent({
+    kind: 27235,
+    content: '',
+    created_at: Math.floor(Date.now() / 1000),
+    tags: [
+      ['u', url],
+      ['method', 'POST'],
+      ['payload', payloadHash],
+    ],
+  });
+
+  const doFetch = (target: string) =>
+    fetch(target, {
+      method: 'POST',
+      headers: {
+        'Content-Type': 'application/nostr+json+rpc',
+        Authorization: `Nostr ${base64(JSON.stringify(authEvent))}`,
+      },
+      body,
+      signal,
+    });
+
+  let res: Response;
+  try {
+    res = await doFetch(url);
+  } catch {
+    // Some WebView/browser contexts block the cross-origin POST. Retry once via
+    // the configured CORS proxy (auth header + body are preserved).
+    const proxied = `https://proxy.shakespeare.diy/?url=${encodeURIComponent(url)}`;
+    res = await doFetch(proxied);
+  }
+
+  if (res.status === 401) {
+    throw new Error(
+      'The relay rejected the request. Your account may not be an owner or ' +
+        'moderator of this relay.',
+    );
+  }
+  if (!res.ok) {
+    throw new Error(`Relay management call failed (HTTP ${res.status}).`);
+  }
+
+  const json = (await res.json()) as Nip86Response<T>;
+  if (json.error) throw new Error(json.error);
+  return json.result as T;
+}
+
+/**
+ * Ask the community relay which NIP-86 methods it supports. Useful to gate the
+ * admin UI (and to confirm the relay speaks NIP-86 at all). Returns [] on any
+ * failure so callers can degrade gracefully.
+ */
+export async function getRelaySupportedMethods(
+  signer: NostrSigner,
+  relayWss: string = SKATE_RELAY,
+  signal?: AbortSignal,
+): Promise<string[]> {
+  try {
+    const methods = await relayManagementCall<string[]>({
+      signer,
+      method: 'supportedmethods',
+      params: [],
+      relayWss,
+      signal,
+    });
+    return Array.isArray(methods) ? methods : [];
+  } catch {
+    return [];
+  }
+}
+
+/**
+ * Remove an event from the community relay's database (NIP-86 `banevent`).
+ * This is a REAL takedown on a relay we control — unlike a NIP-09 kind:5
+ * request, the relay honors it because the caller is an owner/moderator.
+ */
+export async function banEventOnRelay(opts: {
+  signer: NostrSigner;
+  eventId: string;
+  reason?: string;
+  relayWss?: string;
+  signal?: AbortSignal;
+}): Promise<void> {
+  const { signer, eventId, reason, relayWss, signal } = opts;
+  await relayManagementCall({
+    signer,
+    method: 'banevent',
+    params: reason ? [eventId, reason] : [eventId],
+    relayWss,
+    signal,
+  });
+}