feat(nostr): NIP-99 menu listings, NIP-01 profile, NIP-17 stub

nostr/event.py
  Bare NIP-01 NostrEvent with canonical id computation.

nostr/nostr_client.py
  Bidirectional WebSocket client (lifted from events ext, kept
  local). Connects to nostrclient ext's internal relay endpoint,
  dedups by event id (LRU 1000).

nostr_publisher.py
  Builders for:
    * kind 0    — restaurant profile (NIP-01 metadata)
    * kind 30402 — menu item (NIP-99 classified listing,
                              parameterized replaceable by item.id)
    * kind 5    — deletion request (NIP-09)
  Schnorr signing via coincurve (BIP-340).

  Menu listings carry structured price tags (["price", n, currency]),
  status (active|sold) so customers see sold-out items, and 't' tags
  for category, dietary, allergens (allergen:<x>) and ingredients
  (ingr:<x>) so webapps can filter without parsing markdown.

  Restaurants can sign with their own keypair (per-restaurant Nostr
  identity) or fall back to the LNbits Account keypair.

nostr_sync.py
  Subscribes to:
    * kind 30402 #t=menu — backfill 200 + live (echo confirmation
      for now; foreign-menu indexing deferred until we settle on a
      federated cache table).
    * kind 1059 — NIP-17 gift-wrapped DMs, only when
      settings.nostr_orders_enabled. Decryption stubbed (needs
      NIP-44 v2 unwrap); REST stays the supported transport
      until that's wired up. _place_order_from_dm is complete and
      ready for the decryption hook.

nostr/nostr_client.py

@@ -0,0 +1,137 @@
+"""
+Bidirectional Nostr client for the restaurant extension.
+
+Connects to the nostrclient extension's internal WebSocket to publish
+menu listings (NIP-99) and subscribe to incoming order DMs (eventually
+NIP-17). Pattern lifted from the events extension's NostrClient, kept
+local so the two extensions can diverge as needed.
+"""
+
+import asyncio
+import json
+from asyncio import Queue
+from collections import OrderedDict
+from typing import Optional
+
+from loguru import logger
+from websocket import WebSocketApp
+
+from lnbits.helpers import encrypt_internal_message, urlsafe_short_hash
+from lnbits.settings import settings
+
+from .event import NostrEvent
+
+MAX_SEEN_EVENTS = 1000
+
+
+class NostrClient:
+    def __init__(self):
+        self.receive_event_queue: Queue = Queue()
+        self.send_req_queue: Queue = Queue()
+        self.ws: Optional[WebSocketApp] = None
+        self.subscription_id = "restaurant-" + urlsafe_short_hash()[:32]
+        self.running = False
+        self._seen_events: OrderedDict[str, None] = OrderedDict()
+
+    @property
+    def is_websocket_connected(self) -> bool:
+        if not self.ws:
+            return False
+        return self.ws.keep_running
+
+    async def connect(self) -> WebSocketApp:
+        relay_endpoint = encrypt_internal_message("relay", urlsafe=True)
+        ws_url = (
+            f"ws://localhost:{settings.port}"
+            f"/nostrclient/api/v1/{relay_endpoint}"
+        )
+
+        logger.info("[RESTAURANT] Connecting to nostrclient WebSocket...")
+
+        def on_open(_):
+            logger.info("[RESTAURANT] Connected to nostrclient WebSocket")
+
+        def on_message(_, message):
+            try:
+                self.receive_event_queue.put_nowait(message)
+            except Exception as e:
+                logger.error(f"[RESTAURANT] Failed to queue message: {e}")
+
+        def on_error(_, error):
+            logger.warning(f"[RESTAURANT] WebSocket error: {error}")
+
+        def on_close(_, status_code, message):
+            logger.warning(
+                f"[RESTAURANT] WebSocket closed: {status_code} {message}"
+            )
+            self.receive_event_queue.put_nowait(ValueError("WebSocket closed"))
+
+        ws = WebSocketApp(
+            ws_url,
+            on_message=on_message,
+            on_open=on_open,
+            on_close=on_close,
+            on_error=on_error,
+        )
+
+        from threading import Thread
+
+        wst = Thread(target=ws.run_forever)
+        wst.daemon = True
+        wst.start()
+        return ws
+
+    async def run_forever(self):
+        self.running = True
+        while self.running:
+            try:
+                if not self.is_websocket_connected:
+                    self.ws = await self.connect()
+                    await asyncio.sleep(5)
+
+                req = await self.send_req_queue.get()
+                assert self.ws
+                self.ws.send(json.dumps(req))
+            except Exception as ex:
+                logger.warning(f"[RESTAURANT] NostrClient error: {ex}")
+                await asyncio.sleep(60)
+
+    def is_duplicate_event(self, event_id: str) -> bool:
+        if event_id in self._seen_events:
+            return True
+        self._seen_events[event_id] = None
+        if len(self._seen_events) > MAX_SEEN_EVENTS:
+            self._seen_events.popitem(last=False)
+        return False
+
+    async def get_event(self):
+        value = await self.receive_event_queue.get()
+        if isinstance(value, ValueError):
+            raise value
+        return value
+
+    async def publish_nostr_event(self, e: NostrEvent) -> None:
+        await self.send_req_queue.put(["EVENT", e.dict()])
+
+    async def subscribe(self, filters: list[dict]) -> None:
+        self.subscription_id = "restaurant-" + urlsafe_short_hash()[:32]
+        await self.send_req_queue.put(
+            ["REQ", self.subscription_id] + filters
+        )
+        logger.info(
+            f"[RESTAURANT] Subscribed (sub: {self.subscription_id[:20]}...)"
+        )
+
+    async def unsubscribe(self) -> None:
+        await self.send_req_queue.put(["CLOSE", self.subscription_id])
+
+    async def stop(self) -> None:
+        await self.unsubscribe()
+        self.running = False
+        await asyncio.sleep(2)
+        if self.ws:
+            try:
+                self.ws.close()
+            except Exception:
+                pass
+            self.ws = None