docs: update CHANGELOG and PROJECT.md with Market Score page

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

CHANGELOG.md

@@ -6,6 +6,16 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
 ## [Unreleased]
 
+### Added
+- **Market Score methodology page** — standalone page at `/{lang}/market-score`
+  explaining the padelnomics Market Score (Zillow Zestimate-style). Reveals four
+  input categories (demographics, economic strength, demand evidence, data
+  completeness) and score band interpretations without exposing weights or
+  formulas. Full JSON-LD (WebPage + FAQPage + BreadcrumbList), OG tags, and
+  bilingual content (EN professional, DE Du-form). Added to sitemap and footer.
+  First "padelnomics Market Score" mention in each article template now links
+  to the methodology page (hub-and-spoke internal linking).
+
 ### Fixed
 - **Double language prefix in article URLs** — articles were served at
   `/en/en/markets/italy` (double prefix) because `generate_articles()` stored