fix: grant admin role in seed_dev_data so dev-login works immediately

Previously the admin role was only granted during dev-login via
ensure_admin_role(), but dev_run.sh resets the DB on each start,
so the role was never present when first visiting /admin.

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

web/src/padelnomics/scripts/seed_dev_data.py

@@ -308,6 +308,13 @@ def main():
         dev_user_id = cursor.lastrowid
         print(f"  Created (id={dev_user_id})")
 
+    # Grant admin role to dev user
+    conn.execute(
+        "INSERT OR IGNORE INTO user_roles (user_id, role) VALUES (?, 'admin')",
+        (dev_user_id,),
+    )
+    print("  Admin role granted")
+
     # 2. Seed suppliers
     print(f"\nSeeding {len(SUPPLIERS)} suppliers...")
     supplier_ids = {}