fix supplier dashboard UX, Paddle integration, and dev tooling

Supplier dashboard: impersonate redirects to supplier dashboard when user
owns a supplier, sidenav active tab updates on click, listing preview
capped at 420px, insufficient-credits error shows balance and buy CTA,
boost buy buttons resolve Paddle price IDs server-side.

Dev tooling: dev_run.sh kills child processes on Ctrl-C (process
substitution fix), syncs Paddle products to DB on each run,
setup_paddle.py gains --sync mode and fixes Duration/Interval SDK change.

Seed data: each claimed supplier gets its own owner user and subscription.

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

CHANGELOG.md

@@ -13,6 +13,24 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 - **Supplier impersonation** — "Impersonate Owner" button on admin supplier
   detail page; reuses existing `admin.impersonate` route, shown only when
   the supplier has a `claimed_by` user
+- **Seed data: supplier owner accounts** — each claimed supplier now gets its
+  own user + active subscription for realistic impersonation testing
+
+### Fixed
+- **Insufficient credits UX** — unlock error now shows credit balance, cost,
+  and a "Buy Credits" CTA linking to Boost & Upsells tab (was a collapsed
+  red error message with no action)
+- **Supplier dashboard sidenav** — active tab highlight now updates on click
+  (was only correct on initial page load)
+- **Boost/credit buy buttons used wrong price IDs** — dashboard boosts tab
+  passed internal keys (`boost_logo`, `credits_25`) as Paddle `priceId`
+  instead of resolved Paddle price IDs; buttons now show "Not configured"
+  when Paddle products aren't set up
+- **Listing preview card stretched full width** — constrained to 420px to
+  match actual directory card proportions
+- **Impersonate redirects to supplier dashboard** — impersonating a user who
+  owns a supplier now lands on `/suppliers/dashboard` instead of the generic
+  demand-side dashboard
 
 ### Added — Programmatic SEO: Content Generation Engine
 - **Database migration 0010** — `published_scenarios`, `article_templates`,