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/page.tsx

@@ -1,7 +1,20 @@
+import type { Metadata } from "next";
 import Link from "next/link";
 import Image from "next/image";
 import { tripService } from "@/server/services/trip.service";
 import { TripCard } from "@/features/trip/components/trip-card";
+import { siteConfig, siteUrl, absoluteUrl } from "@/lib/site";
+
+export const metadata: Metadata = {
+  title: "Cari Open Trip Pendakian Gunung Bareng",
+  description: `${siteConfig.slogan} ${siteConfig.description}`,
+  alternates: { canonical: "/" },
+  openGraph: {
+    title: `${siteConfig.name} — Open Trip Pendakian Gunung Bareng`,
+    description: siteConfig.slogan,
+    url: "/",
+  },
+};
 
 export default async function HomePage() {
   const trips = await tripService.getOpenTrips();
@@ -25,8 +38,41 @@ export default async function HomePage() {
     .filter((t) => !shownIds.has(t.id) && t.price <= 300000)
     .slice(0, 3);
 
+  const orgJsonLd = {
+    "@context": "https://schema.org",
+    "@graph": [
+      {
+        "@type": "Organization",
+        "@id": `${siteUrl}/#organization`,
+        name: siteConfig.name,
+        url: siteUrl,
+        logo: absoluteUrl("/images/SeTrip.png"),
+        slogan: siteConfig.slogan,
+        description: siteConfig.description,
+      },
+      {
+        "@type": "WebSite",
+        "@id": `${siteUrl}/#website`,
+        url: siteUrl,
+        name: siteConfig.name,
+        description: siteConfig.description,
+        publisher: { "@id": `${siteUrl}/#organization` },
+        inLanguage: "id-ID",
+        potentialAction: {
+          "@type": "SearchAction",
+          target: `${siteUrl}/trips?q={search_term_string}`,
+          "query-input": "required name=search_term_string",
+        },
+      },
+    ],
+  };
+
   return (
     <div className="relative min-h-screen bg-neutral-50">
+      <script
+        type="application/ld+json"
+        dangerouslySetInnerHTML={{ __html: JSON.stringify(orgJsonLd) }}
+      />
       {/* ========== HERO ========== */}
       <section className="relative overflow-hidden bg-neutral-900">
         {/* Logo background full */}