feat: add changelog and versioning, surface it in admin

Bumps version to 0.2.0 (root + apps/web package.json) and adds
CHANGELOG.md as the canonical human-readable history, mirrored by
apps/web/lib/changelog.ts as the in-app data source (single
ChangelogList component renders both).

- /changelog: user-facing page, linked from the account dropdown.
- /admin/changelog: same list, plus a "Version" card on the admin
  overview dashboard linking to it.

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, Monitor, Apple } from "lucide-react";
+import { BookOpen, Calendar, Package, ChefHat, User, Rss, FolderOpen, ShoppingCart, Shield, Search, Compass, Menu, Sun, Moon, Monitor, Apple, History } from "lucide-react";
 import { cn } from "@/lib/utils";
 import { Button, buttonVariants } from "@/components/ui/button";
 import {
@@ -131,6 +131,12 @@ export function Nav() {
               <DropdownMenuItem>
                 <Link href="/settings" className="w-full">{t("settings")}</Link>
               </DropdownMenuItem>
+              <DropdownMenuItem>
+                <Link href="/changelog" className="w-full flex items-center gap-2">
+                  <History className="h-3.5 w-3.5 text-muted-foreground" />
+                  {t("changelog")}
+                </Link>
+              </DropdownMenuItem>
               <div
                 role="group"
                 aria-label={t("systemMode")}