feat: cooking history/gallery, unit conversion, nutrition diary, pantry scan, digest cron, nutrition-targeted meal plans

Six M-sized items from HANDOFF.md's new-features backlog:

- Profile tabs: cooking-history stats (total cooked, last-cooked, streak)
  and a "cooked it" photo gallery, both owner-only
- Display-time unit conversion (metric<->imperial) for recipe ingredients,
  respecting each user's unitPref; original value always shown alongside
  the conversion
- Nutrition daily diary: per-day macro totals computed from cooking history
  x recipe nutritionData, compared against user goals
- Pantry scan: real barcode lookup (zxing + Open Food Facts, no API key)
  with an AI-vision fallback for unbarcoded items, always confirm-before-
  insert, both paths tier/rate-limited like other AI features
- Weekly digest email: new followers/comments/ratings + trending recipes,
  sent via a new `cron` Docker stage (alpine+crond+curl) and `digest-cron`
  compose service hitting a bearer-token-protected internal route
- Meal-plan generation can now target a user's nutrition goals as a
  prompt-level nudge (recipes are AI-invented, not DB-sourced, so this
  can't be a hard macro constraint)

Caught a real deploy-breaking issue while adding the cron stage: appending
it after `runner` silently changed the Dockerfile's default build target,
and `web`'s compose config didn't pin one — fixed by pinning `target:
runner` explicitly. Verified with typecheck, lint, and three separate
`docker build --target` runs (runner/cron/migrator) plus `docker compose
config` validation.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/web/components/layout/nav.tsx

@@ -3,7 +3,7 @@
 import Link from "next/link";
 import { usePathname, useRouter } from "next/navigation";
 import { useTheme } from "next-themes";
-import { BookOpen, Calendar, Package, ChefHat, User, Rss, FolderOpen, ShoppingCart, Shield, Search, Compass, Menu, Sun, Moon } from "lucide-react";
+import { BookOpen, Calendar, Package, ChefHat, User, Rss, FolderOpen, ShoppingCart, Shield, Search, Compass, Menu, Sun, Moon, Apple } from "lucide-react";
 import { cn } from "@/lib/utils";
 import { Button, buttonVariants } from "@/components/ui/button";
 import {
@@ -33,6 +33,7 @@ const NAV_ITEMS = [
   { href: "/feed", key: "feed", icon: Rss },
   { href: "/collections", key: "collections", icon: FolderOpen },
   { href: "/meal-plan", key: "mealPlan", icon: Calendar },
+  { href: "/nutrition", key: "nutrition", icon: Apple },
   { href: "/pantry", key: "pantry", icon: Package },
   { href: "/shopping-lists", key: "shopping", icon: ShoppingCart },
 ] as const;