feat: private accounts, explore/people merge, meal-plan fixes, i18n and theme cleanup

- Private accounts: users.isPrivate hides a user from search and their
  recipes from search/trending/for-you discovery surfaces (follow-aware
  where the route already has session context, blanket exclusion where it
  doesn't); existing followers and direct links are unaffected, no
  follow-request approval flow was built (explicit scope limit)
- Merged /people into the Explore tab (tab=people query param); the old
  standalone route now redirects there
- "Get Ideas" vs "Surprise Me" were doing the same empty-prompt call;
  Surprise Me now injects a real random constraint (5-ingredient, one-pot,
  etc.), matching the existing pattern in the AI recipe-generate dialog
- Meal-plan day cells now link to their recipe (was dead text) and gained
  a one-click "mark as cooked" action
- Theme toggle is now a real three-way light/dark/system control instead
  of a binary flip
- Nutrition goals form had zero i18n wiring; fully localized now

New migration 0027 (users.is_private) generated, left unapplied like the
others. Verified with typecheck, lint, and a clean --no-cache docker build.

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

apps/web/app/(app)/people/page.tsx

@@ -1,22 +1,5 @@
-import type { Metadata } from "next";
-import { headers } from "next/headers";
-import { auth } from "@/lib/auth/server";
-import { PeopleSearch } from "@/components/social/people-search";
-import { getMessages } from "@/lib/i18n/server";
+import { redirect } from "next/navigation";
 
-export const metadata: Metadata = {};
-
-export default async function PeoplePage() {
-  const session = await auth.api.getSession({ headers: await headers() });
-  const m = getMessages((session?.user as { locale?: string } | undefined)?.locale);
-
-  return (
-    <div className="max-w-2xl mx-auto space-y-6">
-      <div>
-        <h1 className="text-2xl font-bold tracking-tight">{m.people.title}</h1>
-        <p className="text-muted-foreground text-sm mt-1">{m.people.subtitle}</p>
-      </div>
-      <PeopleSearch />
-    </div>
-  );
+export default function PeoplePage() {
+  redirect("/explore?tab=people");
 }