Add Spanish and Arabic versions, a contact form captcha and a multilingual sitemap

- English, Spanish (/es) and Arabic (/ar, right to left) versions of every page, with a language switch
- Self-hosted "I'm not a robot" check on the contact form; the message field is optional
- Google Tag Manager, GA4 and Search Console verification in the shared layout
- Sitemap, robots.txt and canonical links point at aigrowthtechnologies.com

scripts/convert-docs.py

@@ -7,7 +7,7 @@ Usage:
 Paragraphs that start with "> " were bold sentences in the deck and render as
 emphasised lines. Each document follows the same conventions: bold all-caps lines are eyebrows
 (when followed by a heading) or CTAs; Heading 1/2/3 give the structure.
-The output lands in src/content/pages/<slug>.json. The homepage is hand-built
+The output lands in src/content/pages/en/<slug>.json. The homepage is hand-built
 and is skipped.
 """
 
@@ -18,7 +18,7 @@ import re
 import sys
 import zipfile
 
-OUT = pathlib.Path(__file__).resolve().parent.parent / "src" / "content" / "pages"
+OUT = pathlib.Path(__file__).resolve().parent.parent / "src" / "content" / "pages" / "en"
 
 # Lines in the decks that are notes to the team, not site copy.
 DROP = [