feat(api): public GET /restaurants/by-slug/{slug}

Prerequisite for the customer webapp module (aiolabs/webapp,
branch feat/restaurant-bundle): the webapp's /r/:slug route needs
to resolve a slug to a Restaurant payload without an admin key.

crud.get_restaurant_by_slug already exists (used by the server-
rendered CMS routes in views.py); just expose it as a public REST
endpoint. Mirrors api_get_restaurant by id and is declared before
the bare-id route so the static prefix wins FastAPI's path match.

Verified live against seeded 'Big Jay's Bustaurant':
  GET /restaurant/api/v1/restaurants/by-slug/big-jays-bustaurant
  -> 200 with the Restaurant payload.

docs/api-reference.md

@@ -15,6 +15,7 @@ the catalog.
 | Method | Path | Notes |
 |---|---|---|
 | `GET` | `/restaurants/{id}` | Restaurant profile |
+| `GET` | `/restaurants/by-slug/{slug}` | Restaurant profile by URL slug — used by webapps that route on `/r/:slug` and need to resolve to an `id` before any other lookup. 404 when no match |
 | `GET` | `/restaurants/{id}/menu` | `{restaurant, tree, items}` — the canonical [[menu-tree|menu tree]] (hydrated children + items per node) plus a flat enriched items list with modifier groups + availability windows pre-joined |
 | `GET` | `/menu_items/{id}` | Single item |
 | `GET` | `/menu_nodes/{id}` | Single node row |

docs/webapp-integration.md

@@ -9,7 +9,17 @@ of restaurants, especially the multi-restaurant cart pattern.
 A webapp can either talk to one restaurant directly or aggregate
 many. There's no central directory inside this extension — grouping
 ("festival", "collective space", "food court") is **emergent** via
-NIP-51 list events curated by whoever runs the venue:
+NIP-51 list events curated by whoever runs the venue.
+
+For the **single-venue** case, a webapp that routes on a URL slug
+(`/r/big-jays-bustaurant`) resolves the slug → restaurant via the
+public `GET /restaurants/by-slug/{slug}` endpoint
+([[api-reference]]) and proceeds with that one `id` for menu reads
+and order placement. Slug is just a URL nicety — internally
+everything continues to key on the restaurant `id`.
+
+For the **aggregator** case (multiple restaurants in one cart), the
+webapp consumes a curated NIP-51 list event:
 
 ```
 {

views_api.py

@@ -59,6 +59,7 @@ from .crud import (
     get_print_job,
     get_print_jobs,
     get_restaurant,
+    get_restaurant_by_slug,
     get_restaurants,
     get_settings,
     move_menu_node,
@@ -248,6 +249,20 @@ async def api_list_restaurants(
     return await get_restaurants(wallet_ids)
 
 
+@restaurant_api_router.get("/api/v1/restaurants/by-slug/{slug}")
+async def api_get_restaurant_by_slug(slug: str) -> Restaurant:
+    """Public — used by the customer webapp to resolve a URL slug
+    (e.g. /r/big-jays-bustaurant) to a restaurant. Mirrors
+    api_get_restaurant; declared *before* the bare-id route so the
+    static prefix wins the path match in FastAPI's router."""
+    restaurant = await get_restaurant_by_slug(slug)
+    if not restaurant:
+        raise HTTPException(
+            status_code=HTTPStatus.NOT_FOUND, detail="Restaurant not found."
+        )
+    return restaurant
+
+
 @restaurant_api_router.get("/api/v1/restaurants/{restaurant_id}")
 async def api_get_restaurant(restaurant_id: str) -> Restaurant:
     """Public — used by the webapp to fetch profile metadata."""