feat(api): keyless unavailable-ranges feed for the guest calendar

GET /api/v1/public/rooms/{id}/unavailable?start=&end= and its RPC twin
chatelet_room_unavailable return the nights a guest cannot book over a
window (default today → +365 d, capped at 400 d): occupying bookings —
live holds included, so the feed always agrees with POST /availability —
and manual blocks, clipped, sorted and coalesced into anonymous half-open
spans. Adjacent spans merge on purpose so a guest cannot tell where one
occupant's dates end and the next begin, nor a block from a stay.

is_available now uses the OCCUPYING_STATUSES constant it was inlining.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

tests/test_unavailable_ranges.py

@@ -0,0 +1,133 @@
+"""Guest calendar feed: merged, anonymous occupied spans for one room."""
+
+import asyncio
+from datetime import datetime, timedelta, timezone
+
+import pytest
+from fastapi import HTTPException
+
+from .. import crud, services, transport_rpcs, views_api
+from ..models import RoomStatus
+from .conftest import make_room
+
+# --- merge_ranges (pure) ---------------------------------------------------
+
+
+def test_merge_sorts_and_coalesces_overlap_and_adjacency():
+    spans = [
+        ("2026-10-10", "2026-10-12"),
+        ("2026-10-01", "2026-10-04"),
+        ("2026-10-04", "2026-10-06"),  # adjacent to the first: one span
+        ("2026-10-11", "2026-10-15"),  # overlaps the 10-12 stay
+    ]
+    out = crud.merge_ranges(spans, "2026-09-01", "2027-09-01")
+    assert out == [("2026-10-01", "2026-10-06"), ("2026-10-10", "2026-10-15")]
+
+
+def test_merge_clips_to_window_and_drops_outside():
+    spans = [
+        ("2026-08-20", "2026-09-05"),  # straddles the window start
+        ("2026-12-28", "2027-01-10"),  # straddles the window end
+        ("2026-07-01", "2026-07-03"),  # entirely before
+        ("2027-02-01", "2027-02-03"),  # entirely after
+    ]
+    out = crud.merge_ranges(spans, "2026-09-01", "2027-01-01")
+    assert out == [("2026-09-01", "2026-09-05"), ("2026-12-28", "2027-01-01")]
+
+
+def test_merge_empty():
+    assert crud.merge_ranges([], "2026-09-01", "2027-01-01") == []
+
+
+# --- services.get_unavailable_ranges ----------------------------------------
+
+
+def _patch(monkeypatch, room, spans):
+    seen: dict = {}
+
+    async def gr(_):
+        return room
+
+    async def occupied(room_id, start, end):
+        seen.update(room_id=room_id, start=start, end=end)
+        return spans
+
+    monkeypatch.setattr(crud, "get_room", gr)
+    monkeypatch.setattr(crud, "get_occupied_ranges", occupied)
+    return seen
+
+
+def test_defaults_to_today_plus_365(monkeypatch):
+    seen = _patch(monkeypatch, make_room("a", status=RoomStatus.active), [])
+    out = asyncio.run(services.get_unavailable_ranges("a"))
+    today = datetime.now(timezone.utc).date()
+    assert out.start == today.isoformat()
+    assert out.end == (today + timedelta(days=365)).isoformat()
+    assert (seen["start"], seen["end"]) == (out.start, out.end)
+    assert out.ranges == []
+
+
+def test_explicit_window_and_shape(monkeypatch):
+    _patch(
+        monkeypatch,
+        make_room("a", status=RoomStatus.active),
+        [("2026-10-05", "2026-10-07")],
+    )
+    out = asyncio.run(services.get_unavailable_ranges("a", "2026-10-01", "2026-11-01"))
+    assert (out.room_id, out.start, out.end) == ("a", "2026-10-01", "2026-11-01")
+    assert [(r.start, r.end) for r in out.ranges] == [("2026-10-05", "2026-10-07")]
+
+
+@pytest.mark.parametrize(
+    ("start", "end"),
+    [
+        ("2026-10-10", "2026-10-10"),  # empty window
+        ("2026-10-10", "2026-10-01"),  # reversed
+        ("2026-01-01", "2027-03-01"),  # > 400 days
+        ("not-a-date", None),
+    ],
+)
+def test_window_validation(monkeypatch, start, end):
+    _patch(monkeypatch, make_room("a", status=RoomStatus.active), [])
+    with pytest.raises(ValueError):
+        asyncio.run(services.get_unavailable_ranges("a", start, end))
+
+
+def test_inactive_room_is_not_found(monkeypatch):
+    _patch(monkeypatch, make_room("a", status=RoomStatus.inactive), [])
+    with pytest.raises(services.NotFound):
+        asyncio.run(services.get_unavailable_ranges("a"))
+
+
+# --- both doors -------------------------------------------------------------
+
+
+def test_http_and_rpc_doors_agree(monkeypatch):
+    _patch(
+        monkeypatch,
+        make_room("a", status=RoomStatus.active),
+        [("2026-10-05", "2026-10-07")],
+    )
+    http = asyncio.run(
+        views_api.api_public_room_unavailable("a", "2026-10-01", "2026-11-01")
+    )
+    rpc = asyncio.run(
+        transport_rpcs.handle_room_unavailable(
+            None,
+            transport_rpcs.NostrRpcRequest(
+                rpc_name="chatelet_room_unavailable",
+                request_id="req-1",
+                body={"room_id": "a", "start": "2026-10-01", "end": "2026-11-01"},
+                sender_pubkey="ab" * 32,
+            ),
+        )
+    )
+    assert rpc == http.dict()
+    assert rpc["ranges"] == [{"start": "2026-10-05", "end": "2026-10-07"}]
+
+
+def test_http_maps_errors(monkeypatch):
+    _patch(monkeypatch, make_room("a", status=RoomStatus.inactive), [])
+    with pytest.raises(HTTPException) as e:
+        asyncio.run(views_api.api_public_room_unavailable("a", None, None))
+    assert e.value.status_code == 404