feat(analytics): add Plausible custom-event markings for six goals

Mark the six conversion goals on the self-hosted Plausible instance so the
events match the goals to be registered in Plausible. Event names verbatim:
Trial, FAQ, Buy, Custom Quote, search posts, Project Plan.

CSS-class markings (work without JS logic, on the clickable element):
- FAQ  -> index/de/es index .faq-card; odoo-hosting-2027 + odoo-community-upgrade
          (de/es twins) and australia <summary>; support.html .faq-question
- Buy  -> index/de/es index .btn-buy anchors; australia + bootcamp native
          post_basket submit buttons (forms stay native POST)

JS call markings in script.js (loaded by index, de/index, es/index):
- Trial        on the successful trial-form POST (.then branch)
- Custom Quote on the successful custom-quote POST (.then branch)
- Project Plan on the successful business-wizard submit
- search posts on the FIRST input of #blogSearch only (guard flag, one per
  pageview, not on every keystroke, not on #ocaSearch)

Nothing fires on page load; the 'Start the free trial' anchors that only
scroll to #trialCard are deliberately not tagged. One goal per topic across
all languages, no language suffix. No visual, behavioural or request change.

australia.html

@@ -431,7 +431,7 @@
           <form method="post" action="https://20.odoo4projects.com/shop/post_basket" target="_blank">
             <input type="hidden" name="basket" value='[{"product_id":4,"qty":1,"info":"Australia"}]' />
             <input type="hidden" name="clear" value="1" />
-            <button type="submit" class="btn btn-brass btn-lg">Get On the Rise — $395 a year</button>
+            <button type="submit" class="btn btn-brass btn-lg plausible-event-name=Buy">Get On the Rise — $395 a year</button>
           </form>
           <a href="odoo-hosting-2027.html" class="btn btn-outline btn-lg">Compare every way to host Odoo</a>
         </div>
@@ -635,7 +635,7 @@
         <h2 class="section-title">Questions the price raises</h2>
         <div class="cmp-faq-grid">
           <details class="cmp-faq">
-            <summary>Where is my data actually stored?</summary>
+            <summary class="plausible-event-name=FAQ">Where is my data actually stored?</summary>
             <div class="cmp-a">
               <p>
                 On our servers in Sydney, Australia. When you choose Australia (Sydney) as your server location,
@@ -645,7 +645,7 @@
             </div>
           </details>
           <details class="cmp-faq">
-            <summary>How much does Odoo hosting cost in Australia?</summary>
+            <summary class="plausible-event-name=FAQ">How much does Odoo hosting cost in Australia?</summary>
             <div class="cmp-a">
               <p>
                 Four plans, all billed yearly in US dollars with tax added at checkout: Side Hustle $ 214.00, On
@@ -656,7 +656,7 @@
             </div>
           </details>
           <details class="cmp-faq">
-            <summary>Do the backups run automatically?</summary>
+            <summary class="plausible-event-name=FAQ">Do the backups run automatically?</summary>
             <div class="cmp-a">
               <p>
                 Yes — backups run on a schedule without you setting anything up. The number of slots depends on
@@ -667,7 +667,7 @@
             </div>
           </details>
           <details class="cmp-faq">
-            <summary>How is this different from odoo.sh?</summary>
+            <summary class="plausible-event-name=FAQ">How is this different from odoo.sh?</summary>
             <div class="cmp-a">
               <p>
                 odoo.sh is Odoo's own hosting, running Odoo Enterprise for a developer workflow — you deploy by
@@ -679,7 +679,7 @@
             </div>
           </details>
           <details class="cmp-faq">
-            <summary>Can I add my own apps, or have something built for me?</summary>
+            <summary class="plausible-event-name=FAQ">Can I add my own apps, or have something built for me?</summary>
             <div class="cmp-a">
               <p>
                 Yes. Odoo's own apps are all there on every plan, and from On the Rise upwards you can add custom
@@ -691,7 +691,7 @@
             </div>
           </details>
           <details class="cmp-faq">
-            <summary>What if I outgrow my plan?</summary>
+            <summary class="plausible-event-name=FAQ">What if I outgrow my plan?</summary>
             <div class="cmp-a">
               <p>
                 You move up without a data migration and without downtime. Upgrade from your Odoo settings and
@@ -701,7 +701,7 @@
             </div>
           </details>
           <details class="cmp-faq">
-            <summary>Do you have Australian support hours, or an Australian office?</summary>
+            <summary class="plausible-event-name=FAQ">Do you have Australian support hours, or an Australian office?</summary>
             <div class="cmp-a">
               <p>
                 No separate Australian support desk is published, and we do not claim an Australian office or
@@ -724,7 +724,7 @@
           <form method="post" action="https://20.odoo4projects.com/shop/post_basket" target="_blank">
             <input type="hidden" name="basket" value='[{"product_id":4,"qty":1,"info":"Australia"}]' />
             <input type="hidden" name="clear" value="1" />
-            <button type="submit" class="btn btn-brass btn-lg">Get On the Rise — $395 a year</button>
+            <button type="submit" class="btn btn-brass btn-lg plausible-event-name=Buy">Get On the Rise — $395 a year</button>
           </form>
           <a href="odoo-hosting-2027.html" class="btn btn-outline btn-lg">Compare every way to host Odoo</a>
         </div>