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>

Dockerfile

@@ -56,3 +56,14 @@ COPY --from=build --chown=nextjs:nodejs /repo/apps/web/.next/static ./apps/web/.
 USER nextjs
 EXPOSE 3000
 CMD ["node", "apps/web/server.js"]
+
+# ---- cron: periodically triggers internal cron endpoints (e.g. weekly digest) ----
+# Minimal alpine + busybox crond image — just curls the running `web` service on a
+# schedule. Doesn't need the app build output at all, so it's based on `base`
+# rather than `runner`, keeping the image tiny and independent of the Next build.
+FROM base AS cron
+RUN apk add --no-cache curl
+COPY docker/cron/crontab /etc/crontabs/root
+COPY docker/cron/run-digest.sh /usr/local/bin/run-digest.sh
+RUN chmod +x /usr/local/bin/run-digest.sh
+CMD ["crond", "-f", "-l", "2"]