feat(admin): product catalog editor

The /_gm console gains a Catalog editor — the source of truth for products.
Create / edit / archive-unarchive products, their atom composition and per-rail
prices (RUB via direct / VOTE via vk / XTR via telegram / CHIP value), and
hard-delete only a never-transacted product (an order or ledger reference forces
archive-only, backed by the FK RESTRICT). The archived flag reuses the existing
product.active. Activation revalidates the sellable shape — a pack (the chips
atom ⇒ a money price per rail, chips-only) or a value (no chips ⇒ a CHIP price);
a tournament-bearing product is composable but never sellable yet.

Backed by payments AdminCatalog / CreateProduct / UpdateProduct /
SetProductActive / DeleteProduct + a pure validateProduct.

Tests: validateProduct (pack / value / tournament / duplicate / shape); the
console editor end to end (create, edit, archive, delete-if-clean, refuse a
transacted delete).

backend/internal/adminconsole/views.go

@@ -653,3 +653,51 @@ type FeedbackDetailView struct {
 	UserTZ           string
 	Banned           bool
 }
+
+// CatalogView is the product-catalog list page.
+type CatalogView struct {
+	Products []ProductRow
+}
+
+// ProductRow is one product in the catalog list: its composition, prices, the archived flag
+// (Active) and the transacted flag (which forbids a hard delete).
+type ProductRow struct {
+	ID         string
+	Title      string
+	Active     bool
+	Atoms      []AtomRow
+	Prices     []PriceRow
+	Transacted bool
+}
+
+// AtomRow is one atom line of a product row.
+type AtomRow struct {
+	Atom     string
+	Quantity int
+}
+
+// PriceRow is one price of a product: the method ("" for a value's CHIP price), the currency, and
+// the amount in that currency's minor units.
+type PriceRow struct {
+	Method   string
+	Currency string
+	Amount   int64
+}
+
+// ProductFormView is the product edit form, pre-filled from the current composition. Atom quantities
+// and prices are flattened to the fixed fields the form offers (0 = absent); Transacted disables the
+// delete action.
+type ProductFormView struct {
+	ID         string
+	Title      string
+	Active     bool
+	Chips      int
+	Hints      int
+	NoAds      int
+	Tournament int
+	PriceRUB   int64
+	PriceVote  int64
+	PriceStar  int64
+	PriceChip  int64
+	Transacted bool
+}