feat(bootcamp): live remaining-seat count from availability webhook

Show the honest remaining seats for product 17 (Bootcamp Q1-2027) on all
three bootcamp pages, in the page's own language, from the availability
webhook. Progressive enhancement (static/bootcamp-availability.js): empty
and hidden by default, filled on a successful fetch; on qty 0 the cohort is
reported full, the next cohort is pointed at, and the Buy buttons are
disabled; on any timeout/error/unexpected payload the page is left exactly
as-is and the Buy buttons stay enabled. The count is never written into the
HTML as a fixed string.

odoo-erp-automation-bootcamp/index.html

@@ -788,6 +788,7 @@
         <h2 class="section-title">Price and booking</h2>
         <p class="bc-price">The programme costs USD 595.00 for all ten sessions.</p>
         <p class="bc-note"><strong>Limited to 6 participants</strong> &mdash; the cohort is capped, so the instructor can work through your own setup.</p>
+        <p class="bc-note bc-seats" data-bc-seats hidden></p>
         <p class="bc-note">A seat can be <strong>transferred at any time</strong>, and <strong>cancelled up to two weeks before</strong> the first session on 21 January 2027.</p>
         <p class="bc-lead">
           Covers the full programme: ten live sessions, one year of hosted Odoo Community Edition, the
@@ -899,6 +900,7 @@
       </div>
     </footer>
     <script defer src="/static/buy.js"></script>
+    <script defer src="/static/bootcamp-availability.js"></script>
     <script defer src="/static/lang.js"></script>
   </body>
 </html>