fix(bootcamp): give the availability fetch a 6s bound (cold-start headroom)

Measured live from the browser: the webhook answers in ~2.2-2.6s warm but a
cold first connection can exceed the old 3s abort, so the count would fall
back to the static text on a fresh visit. 6s is bounded and nothing blocks
the buy either way.

static/bootcamp-availability.js

@@ -22,7 +22,7 @@
     var ENDPOINT = 'https://n8n.odoo4projects.com/webhook/ODOO4projects/available';
     var PRODUCT_ID = 17;
     var CAP = 6;                 /* the page's own cohort cap ("Limited to 6 participants") */
-    var TIMEOUT_MS = 3000;
+    var TIMEOUT_MS = 6000;
 
     /* The page's own words and language. "seat" = seat / Platz / plaza, as used elsewhere
        on the same page ("A seat can be transferred" / "Ein Platz ist übertragbar" /