refactor(http): drop categories/subcategories shim

Remove the transitional layer added in commits 1+2:

models.py
  - Drop Category, Subcategory, CreateCategory, CreateSubcategory.

crud.py
  - Drop create_category / update_category / get_category /
    get_categories / delete_category and the subcategory variants
    along with the _node_row_to_category / _node_row_to_subcategory
    helpers. Tree state is owned exclusively by menu_node CRUD now.

views_api.py
  - Remove old endpoints:
      GET    /api/v1/restaurants/{id}/categories
      POST   /api/v1/categories
      DELETE /api/v1/categories/{id}
      GET    /api/v1/categories/{id}/subcategories
      POST   /api/v1/subcategories
      DELETE /api/v1/subcategories/{id}
    Hits return 404 now.
  - GET /api/v1/restaurants/{id}/menu loses the synthetic
    'categories' projection. Response is {restaurant, tree, items}.

static/js/api.js
  - Drop listCategories / createCategory / deleteCategory and the
    subcategory wrappers.

The CMS menu builder is broken between this commit and commit 4.
The plan acknowledged this trade-off: keeping commits revertible
beats the cost of an unshipped UI page rendering a stale empty
sidebar for one commit's lifetime.

crud.py

@@ -21,15 +21,12 @@ from lnbits.helpers import urlsafe_short_hash
 from .models import (
     MAX_MENU_DEPTH,
     AvailabilityWindow,
-    Category,
     CreateAvailabilityWindow,
-    CreateCategory,
     CreateMenuItem,
     CreateMenuNode,
     CreateModifier,
     CreateModifierGroup,
     CreateRestaurant,
-    CreateSubcategory,
     MenuItem,
     MenuNode,
     MenuNodeRow,
@@ -41,7 +38,6 @@ from .models import (
     Restaurant,
     RestaurantSettings,
     SelectedModifier,
-    Subcategory,
 )
 
 db = Database("ext_restaurant")
@@ -397,129 +393,6 @@ async def delete_menu_node(node_id: str, cascade: bool = False) -> None:
         )
 
 
-# --------------------------------------------------------------------- #
-# Categories / subcategories — transitional shims (drop in commit 3)    #
-# --------------------------------------------------------------------- #
-# These keep the old /categories and /subcategories REST endpoints
-# working over the new menu_nodes table for one commit's lifetime.
-# Drop entirely in the next commit once the new endpoints are live.
-
-
-def _node_row_to_category(row: MenuNodeRow) -> Category:
-    return Category(
-        id=row.id,
-        restaurant_id=row.restaurant_id,
-        name=row.name,
-        description=row.description,
-        sort_order=row.sort_order,
-        image_url=row.image_url,
-        time=row.time,
-    )
-
-
-def _node_row_to_subcategory(row: MenuNodeRow) -> Subcategory:
-    # Subcategory carries the parent category id, not its own restaurant.
-    return Subcategory(
-        id=row.id,
-        category_id=row.parent_id or "",
-        name=row.name,
-        sort_order=row.sort_order,
-        time=row.time,
-    )
-
-
-async def create_category(data: CreateCategory) -> Category:
-    node = await create_menu_node(
-        CreateMenuNode(
-            restaurant_id=data.restaurant_id,
-            parent_id=None,
-            name=data.name,
-            description=data.description,
-            sort_order=data.sort_order,
-            image_url=data.image_url,
-        )
-    )
-    return _node_row_to_category(node)
-
-
-async def update_category(category: Category) -> Category:
-    row = await get_menu_node(category.id)
-    if not row:
-        raise ValueError("Category not found")
-    row.name = category.name
-    row.description = category.description
-    row.sort_order = category.sort_order
-    row.image_url = category.image_url
-    await update_menu_node(row)
-    return category
-
-
-async def get_category(category_id: str) -> Optional[Category]:
-    row = await get_menu_node(category_id)
-    if not row or row.depth != 0:
-        return None
-    return _node_row_to_category(row)
-
-
-async def get_categories(restaurant_id: str) -> list[Category]:
-    rows = await db.fetchall(
-        """
-        SELECT * FROM restaurant.menu_nodes
-        WHERE restaurant_id = :rid AND depth = 0
-        ORDER BY sort_order, time
-        """,
-        {"rid": restaurant_id},
-        model=MenuNodeRow,
-    )
-    return [_node_row_to_category(r) for r in rows]
-
-
-async def delete_category(category_id: str) -> None:
-    await delete_menu_node(category_id, cascade=True)
-
-
-async def create_subcategory(data: CreateSubcategory) -> Subcategory:
-    parent = await get_menu_node(data.category_id)
-    if not parent:
-        raise ValueError("Category not found")
-    node = await create_menu_node(
-        CreateMenuNode(
-            restaurant_id=parent.restaurant_id,
-            parent_id=parent.id,
-            name=data.name,
-            sort_order=data.sort_order,
-        )
-    )
-    return _node_row_to_subcategory(node)
-
-
-async def update_subcategory(subcategory: Subcategory) -> Subcategory:
-    row = await get_menu_node(subcategory.id)
-    if not row:
-        raise ValueError("Subcategory not found")
-    row.name = subcategory.name
-    row.sort_order = subcategory.sort_order
-    await update_menu_node(row)
-    return subcategory
-
-
-async def get_subcategories(category_id: str) -> list[Subcategory]:
-    rows = await db.fetchall(
-        """
-        SELECT * FROM restaurant.menu_nodes
-        WHERE parent_id = :pid
-        ORDER BY sort_order, time
-        """,
-        {"pid": category_id},
-        model=MenuNodeRow,
-    )
-    return [_node_row_to_subcategory(r) for r in rows]
-
-
-async def delete_subcategory(subcategory_id: str) -> None:
-    await delete_menu_node(subcategory_id, cascade=True)
-
-
 # --------------------------------------------------------------------- #
 # Menu items                                                            #
 # --------------------------------------------------------------------- #