feat: trim integration pages from 75 to 25 + migrate to MDX

- Add dedicatedPage flag to integration registry (25 true, 50 false)
- Delete hardcoded nextjs/react/vue/wordpress route pages (wrong metadata)
- Hub page routes non-dedicated integrations to /integrations/script-tag
- Add 301 redirects for 50 removed slugs → /integrations/script-tag
- Migrate guide content from TSX to MDX (content/integrations/*.mdx)
- Add gray-matter, next-mdx-remote, remark-gfm dependencies
- Add content loader (lib/integration-content.ts) matching ciphera-website pattern
- Add prebuild script for integration guide index generation
- Sitemap reduced from 83 to 35 URLs with real lastmod dates
- Remove seoDescription from registry (now in MDX frontmatter)

scripts/generate-integrations.ts

@@ -0,0 +1,44 @@
+import fs from 'fs'
+import path from 'path'
+import matter from 'gray-matter'
+
+const CONTENT_DIR = path.join(process.cwd(), 'content', 'integrations')
+const OUTPUT_PATH = path.join(process.cwd(), 'lib', 'integration-guides.gen.ts')
+
+const files = fs.existsSync(CONTENT_DIR)
+  ? fs.readdirSync(CONTENT_DIR).filter((f) => f.endsWith('.mdx'))
+  : []
+
+const guides: { slug: string; title: string; description: string; category: string; date: string }[] = []
+
+for (const filename of files) {
+  const slug = filename.replace(/\.mdx$/, '')
+  const raw = fs.readFileSync(path.join(CONTENT_DIR, filename), 'utf-8')
+  const { data } = matter(raw)
+  guides.push({
+    slug,
+    title: data.title as string,
+    description: data.description as string,
+    category: data.category as string,
+    date: data.date as string,
+  })
+}
+
+guides.sort((a, b) => a.title.localeCompare(b.title))
+
+const output = `// Auto-generated from content/integrations/*.mdx — do not edit manually
+// Run: npm run generate:integrations
+
+export interface IntegrationGuideSummary {
+  slug: string
+  title: string
+  description: string
+  category: string
+  date: string
+}
+
+export const integrationGuides: IntegrationGuideSummary[] = ${JSON.stringify(guides, null, 2)}
+`
+
+fs.writeFileSync(OUTPUT_PATH, output, 'utf-8')
+console.log(`Generated ${guides.length} integration guides → lib/integration-guides.gen.ts`)