feat: followers-only recipe visibility

Adds a fourth visibility tier alongside private/unlisted/public:
"followers" — visible to the author and anyone who follows them,
excluded from public search/explore/profile listings and from the
anonymous /r/[id] share route, included in the Following feed. The
in-app recipe detail gate and the public share route both check
follow status directly against the DB rather than the union type
alone, since neither previously had any per-viewer access logic for
a non-public/non-owner case.

Requires the generated migration (0041) to run against a live DB —
not applied in this sandbox (no Docker here); run `pnpm db:migrate`.

v0.41.0

apps/web/components/recipe/recipe-card.tsx

@@ -3,7 +3,7 @@
 import Link from "next/link";
 import Image from "next/image";
 import { useTranslations } from "next-intl";
-import { Clock, Users, Lock, Globe, Link2, ExternalLink } from "lucide-react";
+import { Clock, Users, Lock, Globe, Link2, ExternalLink, UserCheck } from "lucide-react";
 import { Badge } from "@/components/ui/badge";
 import { Card, CardContent, CardFooter, CardHeader } from "@/components/ui/card";
 import { getPublicUrl } from "@/lib/storage";
@@ -16,7 +16,7 @@ type Recipe = {
   prepMins: number | null;
   cookMins: number | null;
   difficulty: "easy" | "medium" | "hard" | null;
-  visibility: "private" | "unlisted" | "public";
+  visibility: "private" | "unlisted" | "public" | "followers";
   updatedAt: Date;
   photos?: Array<{ storageKey: string; isCover: boolean }>;
   sourceUrl?: string | null;
@@ -27,6 +27,7 @@ const VISIBILITY_ICON = {
   private: Lock,
   unlisted: Link2,
   public: Globe,
+  followers: UserCheck,
 };
 
 const DIFFICULTY_COLOR = {