Add Equipment page: owned brewers and grinders filter the Brews UI

- user_gear table (migration 008) + GET/PUT /api/gear (brewer keys
  validated against the taxonomy, grinders deduped/trimmed)
- /gear page: silhouette multi-select for owned brewers (autosaves) and
  a grinder list; nav gains Brewing → Equipment
- Brews page: with gear configured, the picker shows only owned brewers
  (plus the edited brew's method) with a show-all toggle; grinder field
  suggests your grinders; empty-gear state links to /gear
- Included in full backups, per-user export, and the OpenAPI spec

Co-Authored-By: Claude Fable 5 <[email protected]>

public/js/nav.js

@@ -19,6 +19,7 @@ const NAV_GROUPS = [
 		items: [
 			{ href: "/brews", icon: "◉", label: "Brews" },
 			{ href: "/beans", icon: "◍", label: "Beans" },
+			{ href: "/gear", icon: "⚒", label: "Equipment" },
 		],
 	},
 	{