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/templates/pages/catalog.gohtml

@@ -0,0 +1,44 @@
+{{define "content" -}}
+<h1>Product catalog</h1>
+{{with .Data}}
+<p class="note">A <strong>pack</strong> funds chips (a money price per rail — RUB via direct, VOTE via vk, XTR via telegram); a <strong>value</strong> buys benefits with chips (a CHIP price). Archived products are hidden from players but still credit an in-flight payment and can be granted. A product with transactions can only be archived, not deleted. Amounts are in minor units (RUB kopecks; VOTE/XTR/CHIP whole). The <code>tournament</code> atom is not sellable yet — keep such a product archived.</p>
+<section class="panel"><h2>Add product</h2>
+<form class="form col" method="post" action="/_gm/catalog">
+<label>Title <input type="text" name="title" maxlength="120" required></label>
+<fieldset><legend>Atoms (quantity; blank = none)</legend>
+<label>Chips <input type="number" name="chips" min="0"></label>
+<label>Hints <input type="number" name="hints" min="0"></label>
+<label>No-ads days <input type="number" name="noads" min="0"></label>
+<label>Tournament <input type="number" name="tournament" min="0"></label>
+</fieldset>
+<fieldset><legend>Prices (minor units; blank = none)</legend>
+<label>RUB — direct (kopecks) <input type="number" name="price_rub" min="0"></label>
+<label>VOTE — vk <input type="number" name="price_vote" min="0"></label>
+<label>XTR — telegram <input type="number" name="price_star" min="0"></label>
+<label>CHIP — value <input type="number" name="price_chip" min="0"></label>
+</fieldset>
+<label><input type="checkbox" name="active" value="true"> Active (on sale)</label>
+<div><button type="submit">Add</button></div>
+</form>
+</section>
+<section class="panel"><h2>Products</h2>
+<table class="list">
+<thead><tr><th>Title</th><th>Status</th><th>Atoms</th><th>Prices</th><th></th></tr></thead>
+<tbody>
+{{range .Products}}
+<tr>
+<td><a href="/_gm/catalog/{{.ID}}">{{.Title}}</a></td>
+<td>{{if .Active}}<span class="ok">active</span>{{else}}<span class="warn">archived</span>{{end}}{{if .Transacted}} <span class="pill">transacted</span>{{end}}</td>
+<td>{{range .Atoms}}<code>{{.Atom}}×{{.Quantity}}</code> {{end}}</td>
+<td>{{range .Prices}}<code>{{.Currency}}{{if .Method}}/{{.Method}}{{end}} {{.Amount}}</code> {{end}}</td>
+<td class="row-actions">
+<form class="form" method="post" action="/_gm/catalog/{{.ID}}/archive"><input type="hidden" name="active" value="{{if .Active}}false{{else}}true{{end}}"><button type="submit">{{if .Active}}Archive{{else}}Unarchive{{end}}</button></form>
+{{if not .Transacted}}<form class="form" method="post" action="/_gm/catalog/{{.ID}}/delete" onsubmit="return confirm('Delete this product? It has never been transacted, so this is safe and permanent.')"><button type="submit">Delete</button></form>{{end}}
+</td>
+</tr>
+{{else}}<tr><td colspan="5"><span class="note">no products</span></td></tr>{{end}}
+</tbody>
+</table>
+</section>
+{{end}}
+{{- end}}

backend/internal/adminconsole/templates/pages/product_detail.gohtml

@@ -0,0 +1,25 @@
+{{define "content" -}}
+{{with .Data}}
+<p class="note"><a href="/_gm/catalog">← all products</a></p>
+<h1>{{.Title}} {{if .Active}}<span class="ok">active</span>{{else}}<span class="warn">archived</span>{{end}}{{if .Transacted}} <span class="pill">transacted</span>{{end}}</h1>
+<section class="panel"><h2>Edit</h2>
+<p class="note">A zero quantity / blank price removes that atom / price. Amounts are in minor units. Saving revalidates the sellable shape when the product is active. Archive / unarchive from the <a href="/_gm/catalog">catalog list</a>.</p>
+<form class="form col" method="post" action="/_gm/catalog/{{.ID}}">
+<label>Title <input type="text" name="title" value="{{.Title}}" maxlength="120" required></label>
+<fieldset><legend>Atoms (quantity; 0 = none)</legend>
+<label>Chips <input type="number" name="chips" min="0" value="{{.Chips}}"></label>
+<label>Hints <input type="number" name="hints" min="0" value="{{.Hints}}"></label>
+<label>No-ads days <input type="number" name="noads" min="0" value="{{.NoAds}}"></label>
+<label>Tournament <input type="number" name="tournament" min="0" value="{{.Tournament}}"></label>
+</fieldset>
+<fieldset><legend>Prices (minor units; 0 = none)</legend>
+<label>RUB — direct (kopecks) <input type="number" name="price_rub" min="0" value="{{.PriceRUB}}"></label>
+<label>VOTE — vk <input type="number" name="price_vote" min="0" value="{{.PriceVote}}"></label>
+<label>XTR — telegram <input type="number" name="price_star" min="0" value="{{.PriceStar}}"></label>
+<label>CHIP — value <input type="number" name="price_chip" min="0" value="{{.PriceChip}}"></label>
+</fieldset>
+<div><button type="submit">Save</button></div>
+</form>
+</section>
+{{end}}
+{{- end}}