feat: extension entrypoint wiring

Ties the layers together: router prefix, static mount, and the permanent
tasks (invoice listener + hold-expiry). Inbound Nostr subscription is
wired-but-commented pending relay plumbing. Extension is now loadable.

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

__init__.py

@@ -0,0 +1,52 @@
+import asyncio
+
+from fastapi import APIRouter
+
+from .crud import db
+from .tasks import expire_holds_loop, wait_for_paid_invoices
+from .views import chatelet_generic_router
+from .views_api import chatelet_api_router
+
+chatelet_static_files = [
+    {
+        "path": "/chatelet/static",
+        "name": "chatelet_static",
+    }
+]
+
+chatelet_ext: APIRouter = APIRouter(prefix="/chatelet", tags=["chatelet"])
+chatelet_ext.include_router(chatelet_generic_router)
+chatelet_ext.include_router(chatelet_api_router)
+
+scheduled_tasks: list[asyncio.Task] = []
+
+
+def chatelet_stop():
+    for task in scheduled_tasks:
+        task.cancel()
+
+
+def chatelet_start():
+    from lnbits.tasks import create_permanent_unique_task
+
+    scheduled_tasks.append(
+        create_permanent_unique_task("chatelet_invoices", wait_for_paid_invoices)
+    )
+    scheduled_tasks.append(
+        create_permanent_unique_task("chatelet_hold_expiry", expire_holds_loop)
+    )
+    # TODO(relay): once relay plumbing lands, also start the inbound Nostr
+    # subscription so guests can query availability + book over Nostr:
+    #   from .nostr.service import subscribe_inbound
+    #   scheduled_tasks.append(
+    #       create_permanent_unique_task("chatelet_nostr_in", subscribe_inbound)
+    #   )
+
+
+__all__ = [
+    "db",
+    "chatelet_ext",
+    "chatelet_start",
+    "chatelet_static_files",
+    "chatelet_stop",
+]