feat(admin): admin grant — raw benefits and by-product reward bundles

The /_gm user card gains a Grant panel: grant raw benefit atoms (hints /
no-ads days / forever) or a defined value product (a reward bundle, including
an archived one), origin-picked. Both write an admin_grant ledger row via
payments.Grant / GrantProduct; the by-product grant records the source
product_id + snapshot. Both refuse a chips atom (never grant currency) or a
tournament atom (no credit target yet); chips/tournament products are also
kept out of the by-product picker.

Tests: the console grant end to end (raw, by-product, refuse a chips pack,
CSRF-guarded).

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

@@ -85,6 +85,26 @@
 {{else}}<p class="note">no ledger entries</p>{{end}}
 {{else}}<p class="note">payments not enabled</p>{{end}}
 </section>
+<section class="panel"><h2>Grant benefits</h2>
+{{if .Grant.Present}}
+<p class="note">A zero-price admin sale of a value — <strong>never chips</strong>. The origin is your compliance choice. The by-product grant applies a defined bundle, including an archived reward product.</p>
+<form class="form col" method="post" action="/_gm/users/{{.ID}}/grant">
+<label>Origin <select name="origin">{{range .Grant.Origins}}<option value="{{.}}">{{.}}</option>{{end}}</select></label>
+<label>Hints <input type="number" name="hints" min="0" value="0"></label>
+<label>No-ads days <input type="number" name="noads" min="0" value="0"></label>
+<label><input type="checkbox" name="forever" value="true"> No-ads forever</label>
+<div><button type="submit">Grant</button></div>
+</form>
+{{if .Grant.Products}}
+<h3>Grant a product</h3>
+<form class="form col" method="post" action="/_gm/users/{{.ID}}/grant-product">
+<label>Origin <select name="origin">{{range .Grant.Origins}}<option value="{{.}}">{{.}}</option>{{end}}</select></label>
+<label>Product <select name="product_id">{{range .Grant.Products}}<option value="{{.ID}}">{{.Title}} ({{.Summary}}){{if .Archived}} — archived{{end}}</option>{{end}}</select></label>
+<div><button type="submit">Grant product</button></div>
+</form>
+{{else}}<p class="note">no grantable products — create a value product in the <a href="/_gm/catalog">catalog</a></p>{{end}}
+{{else}}<p class="note">payments not enabled</p>{{end}}
+</section>
 <section class="panel"><h2>Roles</h2>
 {{$id := .ID}}
 {{if .Roles}}