docs: pricing overhaul + lead-back guarantee — CHANGELOG + PROJECT.md

CHANGELOG: add Added section (guarantee, CRO restructure, credits-only callout,
ROI line) and Changed section (Basic free, card color €59, BP PDF €149,
hero CTA, comparison table, EN/DE translations, setup_paddle.py)

PROJECT.md:
- Correct Done section prices (Growth €199, Pro €499)
- Add Done entries: pricing overhaul, lead-back guarantee
- Add 3 Decisions Log entries (Basic free, guarantee credit-only, static ROI)

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

CHANGELOG.md

@@ -6,6 +6,33 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
 ## [Unreleased]
 
+### Added
+- **Lead-Back Guarantee** — suppliers can claim credits back for non-responding leads
+  with one click after 3 business days. Route `POST /suppliers/leads/<id>/guarantee-claim`,
+  `refund_lead_guarantee()` in credits.py, "Lead didn't respond" button on unlocked
+  lead cards (visible 3–30 days after unlock). Migration 0020 adds `guarantee_claimed_at`
+  and `guarantee_contact_method` columns to `lead_forwards`.
+- **Supplier page CRO restructure** — `/suppliers` page reordered to lead with value
+  before pricing (Why Padelnomics → Lead-Back Guarantee → lead preview → social proof
+  → pricing). All CTAs changed from "See Plans & Pricing" to "Get Started Free".
+- **Static ROI line** — one-sentence ROI callout near pricing grounded in
+  `research/padel-hall-economics.md` data (4-court project = €30K+ contractor profit).
+- **Credits-only callout** — below pricing grid: "Not ready for a subscription? Buy
+  a credit pack and unlock leads one at a time."
+
+### Changed
+- **Basic tier is now free** — `supplier_basic` monthly/yearly price → €0. No Paddle
+  subscription required for Basic. Signup wizard shows "Free forever" instead of €39.
+- **Card color boost** — price corrected €19/mo → €59/mo (aligns with MARKETING.md).
+- **Business plan PDF** — price raised €99 → €149 (KfW-ready document supporting
+  €200K+ investment decision).
+- **Hero and final CTA** — links changed from `#pricing` anchor to direct signup URL.
+- **Comparison table** — €1,799/yr annotated with "(yearly plan)" for clarity.
+- **EN+DE translations** — `sup_meta_desc` updated (removed "from €39/mo"); all
+  Basic-tier strings updated to reflect free tier; FAQ updated with guarantee mention.
+- **`setup_paddle.py`** — Basic subscription products commented out (no longer needed);
+  `boost_card_color` 1900 → 5900 cents; `business_plan` 9900 → 14900 cents.
+
 ### Fixed
 - **Double language prefix in article URLs** — articles were served at
   `/en/en/markets/italy` (double prefix) because `generate_articles()` stored