feat: nostr event layer (builders + sign/publish service)

Implements ADR-0001. kinds.py pins the allocations; events.py has pure
builders (30402 listing, 30078 encrypted reservation, 31923 blocked-range
calendar, 22001 availability response); service.py signs/encrypts via
resolve_signer (spirekeeper hybrid pattern — no nsec at rest) and sketches
publish + inbound subscription. Relay plumbing marked TODO(relay).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019VUQCfdqiLSsFS2jcGnaFD

nostr/events.py

@@ -0,0 +1,119 @@
+"""Builders that turn Chatelet rows into unsigned Nostr events.
+
+These are pure functions: they return unsigned event dicts (kind, tags,
+content) with no pubkey/id/sig. Signing + NIP-44 encryption happen in
+service.py via lnbits.core.signers.resolve_signer, so no nsec is handled
+here and the same code works with a LocalSigner today or a NIP-46 bunker
+later. See docs/event-flow.md for who publishes what, when.
+"""
+
+import json
+
+from ..models import AvailabilityResult, Booking, Room
+from .kinds import (
+    KIND_AVAILABILITY_RESPONSE,
+    KIND_CALENDAR_EVENT,
+    KIND_LISTING,
+    KIND_RESERVATION,
+)
+
+
+def build_listing_event(room: Room) -> dict:
+    """NIP-99 kind:30402 classified listing for a room. Public, signed by
+    the operator's identity. `d` == room.id so re-publishing replaces."""
+    tags = [
+        ["d", room.id],
+        ["title", room.title],
+        ["price", str(room.price_amount), room.price_currency, room.price_frequency],
+        ["status", "active"],
+    ]
+    if room.location:
+        tags.append(["location", room.location])
+    if room.geohash:
+        tags.append(["g", room.geohash])
+    for url in room.images:
+        tags.append(["image", url])
+    for amenity in room.amenities:
+        tags.append(["t", amenity])
+    return {
+        "kind": KIND_LISTING,
+        "content": room.description,
+        "tags": tags,
+    }
+
+
+def build_reservation_event(booking: Booking, guest_pubkey: str) -> dict:
+    """NIP-78 kind:30078 reservation object — the guest's durable, private
+    copy of their booking. `content` MUST be NIP-44 encrypted to the guest
+    by the caller (service.py) before signing; here we return the plaintext
+    payload so the signer can seal it. `d` == booking.id, addressable so
+    status transitions replace in place.
+
+    amount_sat is copied verbatim from the booking (canonical value) — do
+    not recompute it here.
+    """
+    payload = {
+        "booking_id": booking.id,
+        "room_id": booking.room_id,
+        "check_in": booking.check_in,
+        "check_out": booking.check_out,
+        "nights": booking.nights,
+        "num_guests": booking.num_guests,
+        "status": booking.status.value,
+        "amount_sat": booking.amount_sat,
+        "deposit_sat": booking.deposit_sat,
+        "currency": booking.currency,
+        "price_fiat": booking.price_fiat,
+    }
+    return {
+        "kind": KIND_RESERVATION,
+        # placeholder — service.py replaces with NIP-44(payload) for guest
+        "content": json.dumps(payload),
+        "tags": [
+            ["d", booking.id],
+            ["p", guest_pubkey],
+        ],
+        "_plaintext": payload,  # consumed + stripped by service.py before signing
+    }
+
+
+def build_block_calendar_event(
+    room: Room, start_date: str, end_date: str, block_id: str
+) -> dict:
+    """NIP-52 kind:31923 marking a range as unavailable on the room's public
+    calendar. Deliberately carries NO guest PII — just 'these dates are
+    taken'. Only published when settings.publish_availability is true."""
+    return {
+        "kind": KIND_CALENDAR_EVENT,
+        "content": "",
+        "tags": [
+            ["d", f"{room.id}:{block_id}"],
+            ["title", f"{room.title} — unavailable"],
+            ["start", start_date],
+            ["end", end_date],
+            ["a", f"{KIND_LISTING}:{{operator_pubkey}}:{room.id}"],  # link to listing
+        ],
+    }
+
+
+def build_availability_response(
+    result: AvailabilityResult, requester_pubkey: str
+) -> dict:
+    """Aiolabs kind:22001 (ephemeral) reply to an availability query. Content
+    MUST be NIP-44 encrypted to the requester by service.py."""
+    payload = {
+        "room_id": result.room_id,
+        "check_in": result.check_in,
+        "check_out": result.check_out,
+        "available": result.available,
+        "nights": result.nights,
+        "quote_sat": result.quote_sat,
+        "quote_fiat": result.quote_fiat,
+        "currency": result.currency,
+    }
+    return {
+        "kind": KIND_AVAILABILITY_RESPONSE,
+        "content": json.dumps(payload),
+        "tags": [["p", requester_pubkey]],
+        "_plaintext": payload,
+    }