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/trips/page.tsx

@@ -1,13 +1,33 @@
+import type { Metadata } from "next";
 import Link from "next/link";
 import { Suspense } from "react";
 import { tripService } from "@/server/services/trip.service";
 import { TripCard } from "@/features/trip/components/trip-card";
 import { TripFilter } from "@/features/trip/components/trip-filter";
+import { siteConfig } from "@/lib/site";
 
 interface TripsPageProps {
   searchParams: Promise<{ q?: string; from?: string; to?: string }>;
 }
 
+export async function generateMetadata({
+  searchParams,
+}: TripsPageProps): Promise<Metadata> {
+  const { q } = await searchParams;
+  const title = q
+    ? `Open Trip "${q}" — Pendakian Bareng`
+    : "Open Trip Pendakian Gunung — Daftar Trip Aktif";
+  const description = q
+    ? `Hasil pencarian open trip "${q}" di ${siteConfig.name}. Cari open trip pendakian, lihat tanggal, harga, & langsung gabung.`
+    : `Daftar open trip pendakian gunung yang sedang dibuka di ${siteConfig.name}. Pilih trip, lihat itinerary, dan langsung gabung mendaki bareng.`;
+  return {
+    title,
+    description,
+    alternates: { canonical: "/trips" },
+    openGraph: { title, description, url: "/trips" },
+  };
+}
+
 export default async function TripsPage({ searchParams }: TripsPageProps) {
   const params = await searchParams;
   const hasFilters = params.q || params.from || params.to;