feat(seo): add sitemap generator

public/llms.txt

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+# Prabhupāda Says
+
+> The complete teachings of His Divine Grace A.C. Bhaktivedanta Swami Prabhupāda — the books, lectures, conversations, and letters of the Founder-Ācārya of the International Society for Krishna Consciousness (ISKCON) — as structured, searchable, Unicode text (Devanāgarī + IAST transliteration).
+
+All content is server-rendered and crawlable. The full URL list (tens of thousands of pages) is in the sitemap index.
+
+## Sitemap
+
+- [Sitemap index](https://prabhupadasays.org/sitemap.xml): every book, chapter, verse, prose chapter, letter, transcript, essay, magazine, and journal page
+
+## Scriptures (books)
+
+- [All books](https://prabhupadasays.org/books): Bhagavad-gītā As It Is, Śrīmad-Bhāgavatam, Śrī Caitanya-caritāmṛta, Nectar of Devotion, Kṛṣṇa Book, and 30+ more — browsable by chapter and verse (Devanāgarī, transliteration, synonyms, translation, and purport)
+
+## Lectures & conversations
+
+- [Transcriptions](https://prabhupadasays.org/transcriptions): ~3,800 lectures, morning walks, room conversations, and interviews (1966–1977), browsable by year, place, and type
+
+## Letters
+
+- [Letters](https://prabhupadasays.org/letters): ~6,900 letters (1947–1977), browsable by year, recipient, and location
+
+## Reference
+
+- [Glossary](https://prabhupadasays.org/glossary): ~2,750 Sanskrit/Vedic terms
+- [Essays & other documents](https://prabhupadasays.org/essays)
+- [Magazines (Back to Godhead)](https://prabhupadasays.org/magazines)
+- [Journals](https://prabhupadasays.org/journals)
+- [Disciples](https://prabhupadasays.org/disciples)

public/robots.txt

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-User-agent: *
-Disallow: /