chore: remove experimental frontends (web, android, playground, mobile)

Limpieza de los frontends de prueba (SPA React, app Kotlin, gateway playground,
binding gomobile) tras la fase de exploración. El bus (cmd/membershipd + pkg/*)
queda intacto y verde. Empezamos un frontend web nuevo desde cero, construido
de forma incremental. Todo lo borrado permanece en el historial git por si hay
que recuperar algo.

web/src/api.ts

@@ -1,99 +0,0 @@
-// GatewayClient is the SPA's typed wrapper over the unibus gateway HTTP API.
-// Every method is a thin fetch against the gateway, which hosts one real Go bus
-// peer per name and performs all NATS + end-to-end crypto on the browser's
-// behalf. The base URL is chosen at runtime on the connect screen.
-import type { BusEvent, Member, Peer, Room } from "./types";
-
-export class GatewayClient {
-  constructor(public readonly baseURL: string) {
-    // Normalize: drop a trailing slash so `${base}/api/...` never doubles up.
-    this.baseURL = baseURL.replace(/\/+$/, "");
-  }
-
-  private async req<T>(method: string, path: string, body?: unknown): Promise<T> {
-    const res = await fetch(this.baseURL + path, {
-      method,
-      headers: body !== undefined ? { "Content-Type": "application/json" } : undefined,
-      body: body !== undefined ? JSON.stringify(body) : undefined,
-    });
-    const text = await res.text();
-    if (!res.ok) {
-      let msg = text;
-      try {
-        const j = JSON.parse(text);
-        if (j && typeof j.error === "string") msg = j.error;
-      } catch {
-        // not JSON: keep the raw text
-      }
-      throw new Error(msg || `HTTP ${res.status}`);
-    }
-    return (text ? JSON.parse(text) : {}) as T;
-  }
-
-  // connect creates (or recovers) the named peer on the gateway and returns its
-  // public identity. The identity persists across gateway restarts.
-  connect(name: string): Promise<Peer> {
-    return this.req<Peer>("POST", "/api/peer", { name });
-  }
-
-  // peers lists every peer currently hosted by the gateway (for the invite picker
-  // and to label senders by name).
-  peers(): Promise<Peer[]> {
-    return this.req<Peer[]>("GET", "/api/peers");
-  }
-
-  // rooms lists the rooms the named peer knows (created or joined).
-  rooms(peer: string): Promise<Room[]> {
-    return this.req<Room[]>("GET", `/api/rooms?peer=${encodeURIComponent(peer)}`);
-  }
-
-  // members lists the participants of a room.
-  members(roomID: string): Promise<Member[]> {
-    return this.req<Member[]>("GET", `/api/members?room_id=${encodeURIComponent(roomID)}`);
-  }
-
-  // createRoom opens a room on the given subject. encrypt drives both E2E
-  // encryption and per-message signing; the peer is auto-subscribed.
-  createRoom(peer: string, subject: string, encrypt: boolean): Promise<Room & { persist: boolean }> {
-    return this.req("POST", "/api/room", { peer, subject, encrypt, persist: false });
-  }
-
-  // join subscribes the peer to an existing room (must have been invited first
-  // when the room is encrypted).
-  join(peer: string, roomID: string): Promise<{ subject: string; encrypt: boolean }> {
-    return this.req("POST", "/api/join", { peer, room_id: roomID });
-  }
-
-  // invite adds another connected peer (by name) to a room, sealing the room key
-  // to it. Caller must be the room owner.
-  invite(peer: string, roomID: string, target: string): Promise<{ status: string }> {
-    return this.req("POST", "/api/invite", { peer, room_id: roomID, target });
-  }
-
-  // publish sends a text message to a room.
-  publish(peer: string, roomID: string, text: string): Promise<{ status: string }> {
-    return this.req("POST", "/api/publish", { peer, room_id: roomID, text });
-  }
-
-  // kick removes a peer (by name) from a room and rotates the key (forward
-  // secrecy). Caller must be the room owner.
-  kick(peer: string, roomID: string, target: string): Promise<{ status: string }> {
-    return this.req("POST", "/api/kick", { peer, room_id: roomID, target });
-  }
-
-  // stream opens the SSE channel for a peer. onEvent fires for each received bus
-  // message; onError fires if the stream drops. Returns the EventSource so the
-  // caller can close it.
-  stream(peer: string, onEvent: (ev: BusEvent) => void, onError?: () => void): EventSource {
-    const es = new EventSource(`${this.baseURL}/api/stream?peer=${encodeURIComponent(peer)}`);
-    es.onmessage = (e) => {
-      try {
-        onEvent(JSON.parse(e.data) as BusEvent);
-      } catch {
-        // ignore malformed frames (keepalive comments never reach onmessage)
-      }
-    };
-    if (onError) es.onerror = onError;
-    return es;
-  }
-}