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.

index.html

@@ -362,27 +362,27 @@
       <div class="container">
         <h2 class="section-title">Frequently asked questions</h2>
         <div class="faq-grid">
-          <div class="faq-card" onclick="this.classList.toggle('open')">
+          <div class="faq-card plausible-event-name=FAQ" onclick="this.classList.toggle('open')">
             <div class="faq-q"><span>What if I outgrow my plan?</span> <i class="fas fa-chevron-down"></i></div>
             <div class="faq-a"><p>Grow from Side Hustle to Empire without data migration or downtime. Upgrade in your Odoo Settings panel — your instance stays live, your data moves with you.</p></div>
           </div>
-          <div class="faq-card" onclick="this.classList.toggle('open')">
+          <div class="faq-card plausible-event-name=FAQ" onclick="this.classList.toggle('open')">
             <div class="faq-q"><span>Can I customize it?</span> <i class="fas fa-chevron-down"></i></div>
             <div class="faq-a"><p>Yes. On the Rise and above support Git-based modules. Install custom apps, build your own, or use Quick GIT for one-click installs.</p></div>
           </div>
-          <div class="faq-card" onclick="this.classList.toggle('open')">
+          <div class="faq-card plausible-event-name=FAQ" onclick="this.classList.toggle('open')">
             <div class="faq-q"><span>How fast can I get started?</span> <i class="fas fa-chevron-down"></i></div>
             <div class="faq-a"><p>Five minutes. Pick a plan, choose your region — your Odoo instance is live. No setup fee. Stripe payment. Cancel anytime.</p></div>
           </div>
-          <div class="faq-card" onclick="this.classList.toggle('open')">
+          <div class="faq-card plausible-event-name=FAQ" onclick="this.classList.toggle('open')">
             <div class="faq-q"><span>Can I run Odoo Enterprise?</span> <i class="fas fa-chevron-down"></i></div>
             <div class="faq-a"><p>Powerhouse and Empire are Enterprise-ready. Bring your license; we provide the infrastructure.</p></div>
           </div>
-          <div class="faq-card" onclick="this.classList.toggle('open')">
+          <div class="faq-card plausible-event-name=FAQ" onclick="this.classList.toggle('open')">
             <div class="faq-q"><span>ODOO Community? What can it do?</span> <i class="fas fa-chevron-down"></i></div>
             <div class="faq-a"><p>Inventory, accounting, CRM, sales, manufacturing, HR — all in one system. Free and fully open-source.</p></div>
           </div>
-          <div class="faq-card" onclick="this.classList.toggle('open')">
+          <div class="faq-card plausible-event-name=FAQ" onclick="this.classList.toggle('open')">
             <div class="faq-q"><span>Do you have an affiliate program?</span> <i class="fas fa-chevron-down"></i></div>
             <div class="faq-a"><p>No. We believe it is in our best interest to have competitive prices for our shared clients.</p></div>
           </div>
@@ -415,7 +415,7 @@
                 <small class="price-period">/ year</small>
               </div>
               <p class="desc">"ODOO Standard .. that is all my business needs"</p>
-              <a href="javascript:void(0)" class="btn btn-brass btn-buy" data-id="6">Buy Now</a>
+              <a href="javascript:void(0)" class="btn btn-brass btn-buy plausible-event-name=Buy" data-id="6">Buy Now</a>
               <ul>
                 <li><i class="fas fa-check" style="color: var(--success)"></i> Launch Odoo CE in 5 minutes</li>
                 <li><i class="fas fa-check" style="color: var(--success)"></i> Automatic backups — no remembering</li>
@@ -433,7 +433,7 @@
                 <small class="price-period">/ year</small>
               </div>
               <p class="desc">"I need some modules and professional reports"</p>
-              <a href="javascript:void(0)" class="btn btn-brass btn-buy" data-id="4">Buy Now</a>
+              <a href="javascript:void(0)" class="btn btn-brass btn-buy plausible-event-name=Buy" data-id="4">Buy Now</a>
               <ul>
                 <li><i class="fas fa-check" style="color: var(--success)"></i> Launch Odoo CE in 5 minutes</li>
                 <li><i class="fas fa-check" style="color: var(--success)"></i> Automatic backups — no remembering</li>
@@ -452,7 +452,7 @@
                 <small class="price-period">/ year</small>
               </div>
               <p class="desc">"ODOO Enterprise is a must have!"</p>
-              <a href="javascript:void(0)" class="btn btn-brass btn-buy" data-id="5">Buy Now</a>
+              <a href="javascript:void(0)" class="btn btn-brass btn-buy plausible-event-name=Buy" data-id="5">Buy Now</a>
               <ul>
                 <li><i class="fas fa-check" style="color: var(--success)"></i> Launch Odoo CE in 5 minutes</li>
                 <li><i class="fas fa-check" style="color: var(--success)"></i> Automatic backups — no remembering</li>