fix(admin): add missing article_stats route, 500 handler, dev debug mode

- Add /admin/articles/stats HTMX partial endpoint that was referenced
  by article_stats.html but never created (caused 500 during generation)
- Add @app.errorhandler(500) to log exceptions with traceback
- Switch dev_run.sh from Granian to Quart debug mode for browser
  tracebacks and auto-reload

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

web/src/padelnomics/admin/routes.py

@@ -2465,6 +2465,18 @@ async def articles():
     )
 
 
+@bp.route("/articles/stats")
+@role_required("admin")
+async def article_stats():
+    """HTMX partial: article stats bar (polled while generating)."""
+    stats = await _get_article_stats()
+    return await render_template(
+        "admin/partials/article_stats.html",
+        stats=stats,
+        is_generating=await _is_generating(),
+    )
+
+
 @bp.route("/articles/results")
 @role_required("admin")
 async def article_results():

web/src/padelnomics/app.py

@@ -270,6 +270,13 @@ def create_app() -> Quart:
         from .sitemap import sitemap_response
         return await sitemap_response(config.BASE_URL)
 
+    # Ensure unhandled exceptions are always logged (Granian doesn't show
+    # Quart's debug error page, so without this 500s are silent).
+    @app.errorhandler(500)
+    async def handle_500(error):
+        app.logger.exception("Unhandled 500 error: %s", error)
+        return "Internal Server Error", 500
+
     # Health check
     @app.route("/health")
     async def health():