feat(seo): add metadata, sitemap, robots, JSON-LD, dynamic OG image

- Centralize brand/keyword config in lib/site.ts (slogan, 22 keywords).
- Root layout: metadataBase, title template, OG/Twitter defaults, robots rules.
- Per-page metadata: home, trips list (filter-aware), trip detail, profile (noindex).
- Layout wrappers add metadata to client-component pages: login, register, create-trip.
- Trip detail: generateMetadata + JSON-LD Event + BreadcrumbList (price, availability, rating).
- Home page: JSON-LD Organization + WebSite + SearchAction (sitelink search).
- app/sitemap.ts: dynamic sitemap pulling OPEN/FULL trips from Prisma.
- app/robots.ts: disallow /api/, /profile, /create-trip; references sitemap.
- app/trips/[id]/opengraph-image.tsx: dynamic 1200x630 OG image per trip with
  cover photo, title, mountain, date, price, brand badge.
- Seeder: switch trip images from local SVG placeholders to real Unsplash CDN URLs.
- Drop 18 obsolete seed SVGs from public/images/seed/.

New env: NEXT_PUBLIC_SITE_URL (defaults to localhost:3000) — set to prod domain on deploy.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/layout.tsx

@@ -2,6 +2,7 @@ import type { Metadata } from "next";
 import { Geist, Geist_Mono } from "next/font/google";
 import { SessionProvider } from "@/components/providers/session-provider";
 import { Navbar } from "@/components/shared/navbar";
+import { siteConfig, siteUrl } from "@/lib/site";
 import "./globals.css";
 
 const geistSans = Geist({
@@ -15,9 +16,50 @@ const geistMono = Geist_Mono({
 });
 
 export const metadata: Metadata = {
-  title: "SeTrip",
-  description:
-    "Cari open trip pendakian gunung, gabung bareng, nikmati petualangan ke gunung-gunung Jawa Barat.",
+  metadataBase: new URL(siteUrl),
+  title: {
+    default: `${siteConfig.name} — Open Trip Pendakian Gunung`,
+    template: `%s · ${siteConfig.name}`,
+  },
+  description: siteConfig.description,
+  applicationName: siteConfig.name,
+  keywords: [...siteConfig.keywords],
+  authors: [{ name: siteConfig.name }],
+  creator: siteConfig.name,
+  publisher: siteConfig.name,
+  alternates: { canonical: "/" },
+  openGraph: {
+    type: "website",
+    locale: "id_ID",
+    url: "/",
+    siteName: siteConfig.name,
+    title: `${siteConfig.name} — Open Trip Pendakian Gunung`,
+    description: siteConfig.description,
+    images: [
+      {
+        url: "/images/SeTrip.png",
+        width: 1200,
+        height: 630,
+        alt: `${siteConfig.name} — ${siteConfig.slogan}`,
+      },
+    ],
+  },
+  twitter: {
+    card: "summary_large_image",
+    title: `${siteConfig.name} — Open Trip Pendakian Gunung`,
+    description: siteConfig.description,
+    images: ["/images/SeTrip.png"],
+  },
+  robots: {
+    index: true,
+    follow: true,
+    googleBot: {
+      index: true,
+      follow: true,
+      "max-image-preview": "large",
+      "max-snippet": -1,
+    },
+  },
   icons: {
     icon: "/SeTrip.ico",
     apple: "/images/SeTrip.png",